WO2015183538A2 - Poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers and uses thereof - Google Patents

Poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers and uses thereof Download PDF

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Publication number
WO2015183538A2
WO2015183538A2 PCT/US2015/030213 US2015030213W WO2015183538A2 WO 2015183538 A2 WO2015183538 A2 WO 2015183538A2 US 2015030213 W US2015030213 W US 2015030213W WO 2015183538 A2 WO2015183538 A2 WO 2015183538A2
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membrane
acid
alkylene
polydialkylsiloxane
pdms
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PCT/US2015/030213
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French (fr)
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WO2015183538A3 (en
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Nitash P. Balsara
Nikos PETZETAKIS
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The Regents Of The University Of California
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B01D67/0023—Organic membrane manufacture by inducing porosity into non porous precursor membranes
    • B01D67/003—Organic membrane manufacture by inducing porosity into non porous precursor membranes by selective elimination of components, e.g. by leaching
    • B01D67/0031—Organic membrane manufacture by inducing porosity into non porous precursor membranes by selective elimination of components, e.g. by leaching by elimination of at least one of the blocks of a block copolymer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B01D67/0023—Organic membrane manufacture by inducing porosity into non porous precursor membranes
    • B01D67/003—Organic membrane manufacture by inducing porosity into non porous precursor membranes by selective elimination of components, e.g. by leaching
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B01D71/261—Polyethylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/70—Polymers having silicon in the main chain, with or without sulfur, nitrogen, oxygen or carbon only
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/70—Polymers having silicon in the main chain, with or without sulfur, nitrogen, oxygen or carbon only
    • B01D71/701—Polydimethylsiloxane
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
    • B01D71/80—Block polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F283/00—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G
    • C08F283/12—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G on to polysiloxanes
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/42—Block-or graft-polymers containing polysiloxane sequences
    • C08G77/442—Block-or graft-polymers containing polysiloxane sequences containing vinyl polymer sequences
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/15—Use of additives
    • B01D2323/218—Additive materials
    • B01D2323/2182—Organic additives
    • B01D2323/21839—Polymeric additives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/02—Details relating to pores or porosity of the membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
    • B01D61/362—Pervaporation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes

Definitions

  • the present disclosure relates to poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers and uses thereof, including the use of membranes made up of such triblock copolymers for separating organic compounds in an aqueous mixture.
  • Biofuel production from lignocellulosic feedstocks includes degradation of feedstock to fermentable sugars, fermentation of the sugars, and separation of alcohol from the fermentation broth.
  • a distillation process may be used to separate the alcohol from the fermentation broth at the end of the fermentation process, but such process requires intensive energy resources and also suffers from azeotrope formation.
  • Pervaporation may also be used to separate biofuels from dilute aqueous solutions, and can serve as an alternative technique to distillation. Since the alcohol concentration in fermentation broth is typically low ( ⁇ 10%), pervaporation is more economical and practical to separate the alcohol from the other components of the fermentation broth (water, sugar, bacteria and others).
  • Pervaporation is a membrane separation technique that is utilized to separate liquid mixtures through a membrane via a solution-diffusion mechanism. First, permeation through the membrane takes place and then the permeate is collected as a vapor on the other side of the membrane. The evaporation of the permeate on the permeate side of the membrane creates the driving force for the transfer of the permeate.
  • the pervaporation membrane behaves as a selective barrier between the feed and the permeate; therefore, the selection of the pervaporation membrane is crucial to achieve high selectivity and fluxes.
  • the permeability of the components through the membrane is the multiplication of their diffusion and solubility in the membrane material.
  • the diffusivity of water is greater than the diffusivity of the alcohol due to the smaller dimension of the water molecule.
  • a membrane material with higher alcohol solubility may be useful to obtain high alcohol permselectivity.
  • poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers that are suitable for membrane fabrication and/or pervaporation applications.
  • a poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer made up of a polydialkylsiloxane block and polyalkylene end blocks.
  • a triblock copolymer having a structure of formula (I): x-Y-z (I), wherein:
  • X is a polymeric block comprising one or more monomeric units independently having a structure of formula (M x ):
  • Y is a polymeric block comprising one or more monomeric units independently having a structure of formula (M y ):
  • Z is a polymeric block comprising one or more monomeric units independently having the structure of formula (M z ):
  • each R , R , R , R , R and R is independently H, halo, aliphatic or
  • X and Z are polymeric end blocks. Such end blocks may be the same or different. In certain embodiments, X and Z are the same, such that the triblock copolymer may have a structure of formula: X- Y-X or Z- Y-Z.
  • the triblock copolymer has a molecular weight of at least 110 kg/mol. In certain embodiments, the triblock copolymer has a polydialkylsiloxane volume fraction between 0.2 and 0.95. In certain embodiments, the triblock copolymer has a
  • the triblock copolymer has a domain spacing (d) between 10 nm and 90 nm.
  • compositions made up of the triblock copolymers described herein.
  • the composition has less than 35 wt% of polydialkylsiloxane degradants.
  • a method of producing a poly(C t alkylene-b-dialkylsiloxane-b-C t alkylene) triblock copolymer wherein t is an integer greater than or equal to 2.
  • the method includes hydrogenating a poly(C 2t alkadiene-b-dialkylsiloxane-b-C 2t alkadiene) triblock copolymer in the presence of diazene to produce the poly(C t alkylene-b-dialkylsiloxane-b-C t alkylene) triblock copolymer.
  • membranes made up of the triblock copolymers described herein.
  • a membrane made up of a poly(C t alkylene-b-dialkylsiloxane-b-C t alkylene) triblock copolymer. Such membrane may be suitable for separating renewable materials.
  • a membrane made up of: (i) a poly(C t alkylene-b-dialkylsiloxane-b-C t alkylene) triblock copolymer according to any of the embodiments described herein; and
  • a membrane made up of:
  • a membrane including a plurality of poly(alkylene-b- dialkylsiloxane-b-alkylene) triblock copolymers, wherein each triblock copolymer comprises a first polyalkylene end block and a second polyalkylene end block separated by a polydialkylsiloxane block; wherein at least a portion of the plurality of triblock copolymers is aggregated to form one or more polyalkylene-rich microphases and one or more polydialkylsiloxane- rich microphases;
  • the membrane has an actual artificial free volume of between 0.02 and 0.45. In some aspects, the membrane has a ratio of the permeability of one or more organic compounds to the permeability of water of between 1.0 to 4.0. In other aspects, the membrane further includes one or more polydialkylsiloxane homopolymers.
  • a membrane with a non-equilibrium free volume wherein the non-equilibrium free volume is the difference in total free volume measured before annealing and the total free volume measured after annealing.
  • a membrane including a plurality of poly(alkylene- b-dialkylsiloxane-b-alkylene) triblock copolymers and a plurality of polydialkylsiloxane homopolymers, wherein each triblock copolymer comprises a first polyalkylene end block and a second polyalkylene end block separated by a polydialkylsiloxane block; wherein at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of polydialkylsiloxane homopolymers are aggregated to form one or more polyalkylene -rich microphases and one or more polydialkylsiloxane-rich microphases.
  • a method of producing a membrane by: providing a plurality of poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers; providing a plurality of polydialkylsiloxane homopolymers; combining the plurality of triblock copolymers, the plurality of homopolymers, and a first solvent to form a polymer mixture, wherein the first solvent solubilizes at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of homopolymers; and casting the polymer mixture to produce a membrane, wherein the membrane comprises at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of homopolymers.
  • the method further includes contacting the membrane with a second solvent, wherein the second solvent solubilizes at least a portion of the plurality of
  • a poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer comprising a polydialkylsiloxane block and polyalkylene end blocks, wherein the triblock copolymer has a molecular weight of at least 50 kg/mol, and wherein the polyalkylene is optionally substituted with halo.
  • a method of separating one or more organic compounds from an aqueous mixture of organic compounds includes contacting the aqueous mixture with a membrane to separate one or more organic compounds from the aqueous mixture, wherein one or more of the organic compounds in the aqueous mixture selectively permeates through the membrane.
  • the one or more organic compounds are obtained from a renewable or biological source.
  • the ratio of the permeability of the one or more organic compounds to the permeability of water is between
  • the membrane may be according to any of the embodiments described herein.
  • FIG. 1 refers to an exemplary reaction scheme for synthesis of poly(ethylene-b- dimethylsiloxane-b-ethylene) (EDE) triblock copolymers via hydrogenation of poly(l,4- butadiene)-b-polydimethylsiloxane-b-poly(l,4-butadiene) (BDB) using diazene produced via thermolysis of p-toluenesulfonyl hydrazide.
  • FIG. 1 also depicts possible side reactions that may occur based on the starting materials used to synthesize the EDE triblock copolymer.
  • FIG. 2 refers to an exemplary reaction scheme for synthesis of BDB triblock copolymers via sequential anionic polymerization of 1,3-butadiene and
  • FIG. 3A is an exemplary 1H NMR spectrum of triblock copolymer, BDB335-78 (500 MHz, CDC1 3 ).
  • FIG. 3B depicts an exemplary gel permeation chromatograph of PBD32
  • FIG. 4 is an exemplary gel permeation chromatograph of commercially available PDMS homopolymer before and after exposing it to the hydrogenation conditions of Study 2 in Example 2.
  • FIG. 5 depicts an exemplary 1H NMR spectra of hydrogenation products for various reaction conditions described in Table 2 of Example 2 for BDB335-78 (500 MHz, 353 K, d toluene).
  • FIGS. 6A, 6B, and 6C are exemplary high temperature gel permeation chromatographs of BDB335-78.
  • FIG. 6A is before hydrogenation (dashed line) and after hydrogenation under standard conditions (solid line) (entry 1, Table 2 of Example 2).
  • FIG. 6B is before hydrogenation (dashed line) and after hydrogenation under optimized conditions (solid line) (entry 4, Table 2 of Example 2).
  • FIG. 6C is final product under the hydrogenation conditions of entry 6 without additional purification (entry 6, Table 2 of Example 2).
  • FIG. 7 depicts exemplary SAXS profiles of microphase separated EDE triblock copolymers collected at 25 °C, wherein scattering intensity is plotted as a function of the magnitude of the scattering vector, q, and filled triangles represent the primary scattering peaks and the open triangles represent the higher order scattering peaks.
  • FIG. 8 depicts an exemplary graph comparing domain spacing versus total number average block copolymer molecular weight; scaling law d ⁇ M n 0'67 is represented by the solid line.
  • FIGS. 9A and 9B depict exemplary graphs for ethanol (FIG. 9A) and water (FIG. 9B) permeabilities normalized by PDMS volume fraction as a function of PDMS volume fraction.
  • FIG. 10 depicts an exemplary graph showing ethanol/water selectivity as a function of PDMS volume fractions.
  • FIGS. 11A and 11B depict exemplary graphs showing ethanol (FIG. 11A) and water (FIG. 11B) permeabilities normalized by PDMS volume fraction and morphology factor as a function of PDMS volume fraction.
  • FIGS. 12A and 12B depict exemplary graphs showing ethanol (FIG. 12A) and butanol (FIG. 12B) permeabilities for membranes fabricated by EDE397-61 with different amounts of transporting volume fraction, wherein circles show the effect of extra free volume, and triangles show the effect of extra PDMS volume.
  • FIG. 13 depicts an exemplary graph showing butanol/water selectivity (circle) and ethanol/water selectivity (triangle) for membranes fabricated by EDE397-61 (from Example 3) with different amounts of free volume.
  • BuOH refers to butanol
  • EtOH refers to ethanol.
  • FIG. 14 depicts exemplary thermogravimetric analysis (TGA) data for the
  • FIG. 15 depicts an exemplary DSC graph showing the second heating/cooling cycle of EDE340-77.
  • FIG. 16 depicts an exemplary wide angle x-ray scattering (WAXS) profile of EDE340-77 showing the characteristic Bragg peaks of crystalline polyethylene domains.
  • WAXS wide angle x-ray scattering
  • FIG. 17 depicts a process to form a membrane from EDE triblock copolymers.
  • FIG. 18 depicts a process to increase the total actual free volume ($ rans after) in an EDE triblock copolymer membrane.
  • FIG. 19 depicts a flow diagram of a process to produce an EDE triblock copolymer membrane with actual artificial free volume (AFV)-
  • FIG. 20A depicts a plot of small angle X-ray scattering data for a series of EDE129- 41 triblock copolymer membranes constructed using different levels of PDMS homopolymer.
  • the data for the composite membranes were collected after removing the PDMS homopolymer via washing.
  • the filled arrows indicate the primary peak.
  • FIG. 20B depicts a plot of small angle X-ray scattering data for a series of EDE209- 45 triblock copolymer membranes constructed using different levels of PDMS homopolymer.
  • the data for the composite membranes were collected after removing the PDMS homopolymer via washing.
  • the filled arrows indicate the primary peak, and the hollow arrows indicate the higher order peaks.
  • FIG. 21A depicts a scanning transmission electron microscopy (STEM) image of cyro-microtomed sample of a membrane composed of EDE129-41. The image was collected by a high-angle annular dark field detector.
  • STEM scanning transmission electron microscopy
  • FIG. 21B depicts a scanning transmission electron microscopy (STEM) image of cyro-microtomed sample of a membrane composed of EDE129-41/17. The image was collected by a high-angle annular dark field detector.
  • STEM scanning transmission electron microscopy
  • FIG. 22A depicts a plot of free- volume cavity size distributions for membranes composed of EDE129-41, EDE129-41/9 and EDE129-41/17. The inset shows a magnification of the large cavity size population. The data was obtained using positron annihilation lifetime spectroscopy (PALS).
  • FIG. 22B depicts a plot of the relative intensity of the large free- volume cavity size population as a function of the amount of homopolymer blended and washed away for membranes composed of EDE129-41, EDE129-41/9 and EDE129-41/17. The data was obtained using positron annihilation lifetime spectroscopy (PALS).
  • PALS positron annihilation lifetime spectroscopy
  • FIG. 22C depicts a plot of the relative intensity of the small free-volume cavity size population as a function of the amount of homopolymer blended and washed away
  • FIG. 23 depicts a plot of normalized butanol permeability (right y-axis) and normalized ethanol permeability (left y-axis) as a function of theoretical artificial free volume (/ADD, top x-axis) and actual artificial free volume (/AFV, bottom x-axis), for a series of membranes composed of EDE129-41, EDE129-41/9 and EDE129-41/17.
  • the circles with error bars are butanol permeability by the EDE membranes
  • the squares with error bars are ethanol permeability by the EDE membranes
  • the black circle without error bars is butanol permeability by a cross-linked PDMS membrane
  • the black square without error bars is the ethanol permeability by a cross-linked PDMS membrane.
  • FIG. 24 depicts a plot of the ratio of butanol selectivity to water selectivity (left y- axis) and the ratio of butanol selectivity to water selectivity (right y-axis) as a function of theoretical artificial free volume ( ADD, top x-axis) and actual artificial free volume (/AFV, bottom x-axis), for a series of EDE triblock copolymer membranes.
  • the circles with error bars are butanol/water selectivity by the EDE membranes
  • the squares with error bars are ethanol/water selectivity by the EDE membranes
  • the black circle without error bars is the butanol/water selectivity by a cross-linked PDMS membrane
  • the black square without error bars is the ethanol/water selectivity by a cross-linked PDMS membrane.
  • BuOH refers to butanol
  • EtOH referes to ethanol.
  • FIG. 25A depicts a plot of ethanol permeability as a function of actual artificial free volume (/AFV) for a series of EDE membranes.
  • FIG. 25B depicts a plot of butanol permeability as a function of actual artificial free volume (/AFV) for a series of EDE membranes.
  • FIG. 26 depicts a plot of the PALS intensity as a function of cavity diameter for a polyetheylene (PE) homopolymer.
  • FIG. 27 depicts a plot of actual additional free- volume ( AFV) as a function of theoretical additional free volume (/ADD) for a series of EDE block copolymer membranes.
  • triblock copolymers that may be suitable for selectively separating one or more organic compounds from an aqueous mixture.
  • the triblock copolymers provided herein may be used to selectively separate certain alcohols from a fermentation product mixture.
  • block copolymer includes polymers that include at least two blocks, where each block contains different polymerized monomer type(s) than the adjacent block or blocks.
  • a "diblock copolymer” may include a polymerized block A and an adjacent polymerized block B, represented as A-B.
  • a "triblock copolymer” may include two polymerized end blocks A flanking a middle polymerized block B, represented as A-B-A.
  • a triblock copolymer may contain three different polymerized blocks represented as A-B-C.
  • a poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer made up of a polydialkylsiloxane block and polyalkylene end blocks.
  • the polyalkylene end blocks may be the same or different.
  • such triblock copolymer may have a A-B-A pattern, with a polydialkylsiloxane middle block B and polyalkylene end blocks A flanking the middle block.
  • such triblock copolymer may have an A-B-C pattern, with a polydialkylsiloxane middle block B and polyalkylene end blocks A and C flanking the middle block.
  • the polyalkylene is polyethylene, polypropylene, polyisoprene or polybutadiene. In certain embodiments, the polyalkylene is optionally substituted with halo. In one embodiment, the polyalkylene is optionally substituted with fluoro. In other embodiments, the polydialkylsiloxane is polydimethylsiloxane.
  • a triblock colpolymer having a structure of formula (I): x-Y-z (I), wherein:
  • X and Z are polyalkylene end blocks
  • Y is a polydialkylsiloxane block.
  • X comprises one or more monomeric units independently having a structure of formula
  • Y comprises one or more monomeric units independently having a structure of formula
  • Z comprises one or more monomeric units independently having the structure of formula each R , R , R , R , R and R is independently H, halo, aliphatic or
  • the polymeric end blocks may be the same or different.
  • X and Z are the same, such that the triblock copolymer may have a structure of formula: X-Y-X or
  • X, Y and/or Z may, in certain embodiments include two or more monomeric units.
  • X, Y and/or Z include two or more monomeric units, such monomeric units within a given polymeric block may be randomly arranged.
  • R YB , R ZA and R ZB is independently H, halo, alkyl or haloalkyl.
  • each R XA , R XB , R YA , R YB , R ZA and R ZB is independently H, F, CH 3 , CF 3 , CH 2 CH 3 , CH 2 CH 2 CH 3 ,
  • each X and Z is a polymeric block independently comprising one or more monomeric units selected from:
  • the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer is a poly(ethylene-b-dialkylsiloxane-b-ethylene) triblock copolymer.
  • each X and Z comprises monomeric unit:
  • the triblock copolymer has a structure of formula (A): wherein: each R a , R b , R c and R d is independently OR 1 , NR X R 2 , alkyl, haloalkyl, CN, or H, wherein each R 1 and R 2 is independently H, alkyl or haloalkyl; and each R and R is independently H, halo, aliphatic or haloaliphatic.
  • the triblock copolymer has a structure of formula (Al):
  • m, n and p refers to the number of repeating units for a given polymeric block. In some embodiments, m and p may be the same.
  • a polyethylene block (or hydrogenated polybutadiene) with number average molecular weight 56kDa has an m or p value of 1000, since the repeated unit in hydrogenated polybutadiene has molecular weight of 56.
  • n refers to the average number of repeated units in the polydialkylsiloxane block, wherein: number of repeating units in polydialkylsiloxane block
  • polydialkylsiloxane block For example, a polydimethylsiloxane (PDMS) block with number average molecular weight of
  • 74kDa has an n of 1000, since the repeated unit in PDMS has a molecular weight of 74.
  • the number of units in each block may be determined by any suitable methods known in the art, including for example 1H NMR spectroscopy.
  • the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer is a poly(propylene-b-dialkylsiloxane-b-propylene) triblock copolymer.
  • each X and Z comprises monomeric unit:
  • the triblock copolymer has a structure of formula (B):
  • each R a , R b , R c and R d is independently OR 1 , NR X R 2 , alkyl, haloalkyl, CN, or H, wherein each R 1 and R 2 is independently H, alkyl or haloalkyl; and each R and R is independently H, halo, aliphatic or haloaliphatic.
  • the triblock copolymer has a structure of formula (Bl):
  • m, n and p refers to the number of repeating units for a given polymeric block. In some embodiments, m and p may be the same.
  • the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer is a poly(butadiene-b-dialkylsiloxane-b-butadiene) triblock copolymer.
  • each X and Z is a polymeric block comprising monomeric units:
  • a polymeric block includes two or more monomeric units, such two or more monomeric units may be randomly arranged in the block. Further, it should be understood that the two or more monomeric units may be present in certain ratios. For exam le in some variations, these monomeric units are present in a ratio of is between 0.1 to 0.9 and 0.07 to 0.93.
  • the triblock copolymer has a structure of formula (C):
  • each R a , R b , R c and R d is independently OR 1 , NR X R 2 , alkyl, haloalkyl, CN, or H, wherein each R 1 and R 2 is independently H, alkyl or haloalkyl; each R and R is independently H, halo, aliphatic or haloaliphatic; and a and b refer to the number of monomeric units in a polymeric block.
  • the ratio of a : b is between 0.1 : 0.9 and 0.07 : 0.93.
  • the triblock copolymer has a structure of formula (CI):
  • the monomeric units may be randomly arranged in the ends blocks of triblock polymer (C) and (CI). It should further be understood that in formula (C) and (CI) above, m, n and p refers to the number of repeating units for a given polymeric block. In some embodiments, m and p may be the same.
  • the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer is a poly(isoprene-b-dialkylsiloxane-b-isoprene) triblock copolymer.
  • each X and Z is a polymeric block comprising monomeric units:
  • a polymeric block includes two or more monomeric units, such two or more monomeric units may be randomly arranged in the block. Further, it should be understood that the two or more monomeric units may be present in certain ratios. For example, in some variations, these monomeric units are present in a ratio of
  • each R a , R b , R c and R d is independently OR 1 , NR X R 2 , alkyl, haloalkyl, CN, or H, wherein
  • each R and R is independently H, alkyl or haloalkyl; each R and R is independently H, halo, aliphatic or haloaliphatic; and a, b and c refer to the number of monomeric units in a polymeric block.
  • the ratio of a + b : c is between 0.1 : 0.9 and 0.07 : 0.93.
  • the triblock copolymer has a structure of formula (Dl):
  • the monomeric units may be randomly arranged in the ends blocks of triblock polymer (D) and (Dl). It should further be understood that in formula (D) and (Dl) above, m, n and p refers to the number of repeating units for a given polymeric block. In some embodiments, m and p may be the same.
  • each R a , R b , R c and R d is independently OH, NH 2 , C(CH 3 ) 3 , CN, or H.
  • Aliphatic refers to a linear or branched hydrocarbon structure, and can be saturated or have any degree of unsaturation.
  • Aliphatic groups include, for example, alkyl, alkenyl, and alkynyl.
  • an aliphatic group has I to 10 carbon atoms (i.e. , Ci-io aliphatic group), 1 to 9 carbon atoms (i.e. , C1-9 aliphatic group), 1 to 8 carbon atoms (i.e. , C 1-8 aliphatic group), 1 to 7 carbon atoms (i.e. , Cj . . 7 aliphatic group), 1 to 6 carbon atoms (i.e. , C] .
  • alkyl refers to a linear or branched saturated hydrocarbon chain.
  • alkyl has 1 to 10 carbon atoms (i.e. , CMO alkyl), 1 to 9 carbon atoms (i.e. , C1 -9 alkyl), 1 to 8 carbon atoms (i.e. , C 1-8 alkyl), 1 to 7 carbon atoms (i.e. , C 1-7 alkyl), 1 to 6 carbon atoms (i.e. , ⁇ .. alkyl), 1 to 5 carbon atoms ⁇ i.e., Q.5 alkyl), 1 to 4 carbon atoms (i.e. , C3 ⁇ 4..
  • alkyl 1 to 3 carbon atoms (i.e. , C 1-3 alkyl), 1 to 2 carbon atoms (i.e. , C 1-2 alkyl), or 1 carbon atom (i.e. , C t alkyl),
  • alkyl groups include methyl, ethyl, n-propyl, jso-propyl, n-butyl, sec- butyl, ;3 ⁇ 4r/-butyl, ra-pentyl, 2-pentyl, wo-pentyl, weo-pentyl, hexyl, 2 -hexyl, 3-hexyl, and 3- methylpentyl.
  • W hen an alkyl residue having a specific number of carbons is named, all geometric isomers having that number of carbons may be encompassed; thus, for example, "butyl” can include w-butyl, sec- butyl, so -butyl and tert-butyl; “propyl” can include ⁇ .-propyl and so-propyl.
  • alkenyl refers to a linear or branched hydrocarbon chain with one or more double bonds.
  • alkenyl has 2 to 10 carbon atoms (i.e., C 2-1 o alkenyl), 2 to 10 carbon atoms (i.e. , C 2 -9 alkenyl), 2 to 8 carbon atoms (i.e. , C 2 -s alkenyl), 2 to 7 carbon atoms (i.e. , C 2 -7 alkenyl), 2 to 6 carbon atoms (i.e. , C 2 -6 alkenyl), 2 to 5 carbon atoms (i.e. , C 2 -5 alkenyl), 2 to 4 carbon atoms (i.e. , C 2- 4 alkenyl), or 2 or 3 carbon atoms (i.e. , C 2 -3 alkyl).
  • alkynyl refers to a linear or branched hydrocarbon chain with one or more triple bonds.
  • alkynyl has 2 to 10 carbon atoms (i.e. , C 2 _io alkynyl), 2 to 10 carbon atoms (i.e. , C 2 - 9 alkynyl), 2 to 8 carbon atoms (i.e. , C 2 _8 alkynyl), 2 to 7 carbon atoms (i.e. , C 2 _7 alkynyl), 2 to 6 carbon atoms (i.e. , C 2 _6 alkynyl), 2 to 5 carbon atoms (i.e. , C 2 _5 alkynyl), 2 to 4 carbon atoms (i.e. , C 2 _ 4 alkynyl), 2 or 3 carbon atoms (i.e. , C 2 _ 3 alkynyl).
  • Haloaliphatic refers a linear or branched hydrocarbon structure, and can be saturated or have any degree of unsaturation, wherein one or more hydrogen atoms are replaced by a halogen.
  • haloalkyl refers to a linear or branched saturated hydrocarbon chain, wherein one or more hydrogen atoms are replaced by a halogen.
  • haloalkenyl and
  • haloalkynyi refer to a linear or branched hydrocarbon chain with one or more double bonds, or one or more triple bonds, respectively, wherein one or more hydrogen atoms are replaced by a halogen.
  • the halogen group may be, but are not necessarily, the same halogen; thus, for example, difluoroalkyl, chloro-fluoro- alkyl is within the scope of dihaloalkyl.
  • Other examples of a haloalkyl group include
  • polyethylene-polydimethylsiloxane-polyethylene As used herein, the terms "polyethylene-polydimethylsiloxane-polyethylene,” “ethylene-dimethylsiloxane-ethylene,” “poly(ethylene-b-dimethylsiloxane-b-ethylene),” “PE-b- PDMS-b-PE,” “PE-PDMS-PE,” and “EDE” may be used interchangeably and refer to triblock copolymers including three segments or sections: a polydimethylsiloxane middle block and polyethylene end blocks flanking the middle block. Triblock Copolymers Properties
  • poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein may have one or more of the following properties.
  • the triblock copolymers described herein have a molecular weight of at least 110 kg/mol, or between 110 kg/mol and 1000 kg/mol, or between 110 kg/mol and 500 kg/mol. In some embodiments, the triblock copolymers described herein have a molecular weight of at least 50 kg/mol, or between 50 kg/mol and 1000 kg/mol, or between 50 kg/mol and 500 kg/mol, or between 50 kg/mol and 400 kg/mol.
  • the molecular weight of a triblock copolymer is a number average molecular weight:
  • the number average molecular weight is one way of describing the molecular weight of a polymer.
  • the number average molecular weight is the arithmetic mean or average of the molecular masses of the individual units.
  • the number average molecular weight may be determined by measuring the molecular weight of N polymer molecules, summing the masses, and dividing by N.
  • the number average molecular weight of a polymer can be determined by gel permeation chromatography, viscometry (e.g., via the Mark-Houwink equation), colligative methods (e.g., vapor pressure osmometry), end-group determination or proton NMR.
  • the triblock copolymers described herein have a
  • polydialkylsiloxane volume fraction between 0.2 and 0.95, between 0.2 and 0.8, or between 0.6 and 0.95.
  • volume fraction of block A ( ⁇ ⁇ ) is the volume occupied by block A over the total volume of the block copolymer.
  • the volume occupied by block A (V A ) is the product of the volume of each repeated unit for block A times the average number of repeated units of block A
  • V A (nxvolume of repeat unit)/0.1
  • V B (mxvolume of repeat unit)/0.1
  • the volume fraction of a triblock copolymer For example, the volume fractions of the PDMS block of the BDB and EDE copolymers ( P DMS ) were determined using monomer volumes of 0.111, 0.138 and 0.119 nm for PBD, PDMS and PE respectively.
  • the triblock copolymers described herein have a ⁇ PDMS between 0.2 and 0.95, between 0.2 and 0.8, or between 0.6 and 0.95.
  • the triblock copolymers described herein have a morphology capable of providing a continuous transporting phase.
  • transporting phase refers to the polydialkylsiloxane-rich microphases.
  • One of skill in the art would recognize that the polydialkylsiloxane and the polyalkylenes are immiscible, and hence the corresponding block copolymers microphase separate and form polydialkylsiloxane-rich microphases polyalkylenes-rich microphases. Microphases may also be referred to as "microdomains.”
  • continuous transporting phase refers to the microphase volume fraction with a morphology factor of 1, whereby the morphology factor is a measure of the impedance to transport relative to the transporting phase.
  • the impedance measurement may be the same as in the transporting phase.
  • continuous transporting phase refers to the microphase volume fraction that will have the same or greater permeability as the PDMS homopolymer, which is similar to the transporting phase.
  • continuous transporting phase may be measured by small-angle X-ray scattering, electron microscopy.
  • the triblock copolymer has a cylindrical, lamellar, double diamond, or gyroid morphology. In one embodiment, the triblock copolymer has a cylindrical or lamellar morphology. In another embodiment, the triblock copolymer has a cylindrical morphology. In yet another embodiment, the triblock copolymer has a lamellar morphology.
  • “lamellar morphology” includes a phase domain morphology having layers of alternating compositions that generally are oriented parallel with respect to one another. In some embodiments, the domain size is 15-100 nm. In some embodiments, the morphologies are bicontinuous. The term “lamellar morphology” also includes performated lamellae.
  • cylindrical morphology includes a phase domain morphology having discrete tubular or cylindrical shapes.
  • the tubular or cylindrical shapes may be hexagonally packed on a hexagonal lattice.
  • the domain size is 15-100 nm.
  • the morphologies are bicontinuous.
  • centroid morphology includes a phase domain morphology having a network structure with triply connected junctions.
  • the domain size is 15-100 nm.
  • the morphologies are bicontinuous.
  • double diamond morphology includes a phase domain morphology having a double-diamond symmetry of space group Pn3m.
  • the domain size is 15-100 nm.
  • the morphologies are bicontinuous.
  • the triblock copolymers described herein have a domain spacing (d) between 10 nm and 90 nm, or between 20 nm and 90 nm.
  • Domain spacing refers to the size of the repeating feature in the microphase separated-material.
  • domain spacing may be measured by X-ray scattering, electron microscopy.
  • the triblock copolymer loses about 5% of weight at a temperature between 400°C and 560°C.
  • the triblock copolyers described herein may have one or a combination of the properties described above.
  • the poly(ethylene-b-dialkylsiloxane-b-ethylene) triblock copolymer has:
  • the poly(ethylene-b-dialkylsiloxane-b-ethylene) triblock copolymer has:
  • composition made up of any of the triblock copolymers described herein.
  • the composition has less than 35 wt , less than 30 wt , less than 25 wt , less than 20 wt , less than 15 wt% or less than 10 wt of polydialkylsiloxane degradants.
  • Such degradants may include, for example, poly(dimethylsiloxane) with terminal groups selected from hydroxyl, amino, tert-butyl, nitrile, and H.
  • the degradants have a structure of formula (X):
  • R and R are as defined in formula (I) above; and R e is OR 1 , NR X R 2 , alkyl, haloalkyl, CN, or H, wherein each R 1 and R 2 is independently
  • poly(alkylene-b-dialkylsiloxane-b- alkylene) triblock copolymers described herein are also methods of producing the poly(alkylene-b-dialkylsiloxane-b- alkylene) triblock copolymers described herein.
  • the approaches for synthesizing polyalkylene, such as polyethylene (PE), and polydialkylsiloxane, such as polydimethylsiloxane (PDMS) known in the art are typically incompatible.
  • PE may be synthesized by metal catalysis
  • PDMS may be synthesized by condensation or ring opening polymerization.
  • the methods provided herein address this challenge by providing methods to produce poly(C t alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymers.
  • process 1100 is an exemplary reaction to produce poly(ethylene-b-dialkylsiloxane-b-ethylene) (EDE) triblock copolymer 120, wherein R YA and R YB are independently H, halo, aliphatic or haloaliphatic, and R a , R b , R c and R d are
  • each R 1 and R2 is independently H, alkyl or haloalkyl.
  • process 1100 may generally be applied to other types of poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein, including any poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers that may optionally be substituted with one or more halogen atoms, and one of skill in the art would recognize how to make the appropriate modifications.
  • Process 1100 involves hydrogenation of poly(l,4-butadiene)-b-polydimethylsiloxane- b-poly(l,4-butadiene) (BDB) 120 in the presence of diazene 110.
  • BDB poly(l,4-butadiene)-b-polydimethylsiloxane- b-poly(l,4-butadiene)
  • the BDB copolymer has a concentration of less than 5 wt , less than 2wt% or less than 1 wt .
  • the BDB copolymer is hydrogenated in the presence diazene and solvent.
  • the BDB copolymer is soluble in the solvent at a temperature of at least 50°C, or between 65°C and 75°C.
  • the solvent may include an aromatic solvent.
  • the solvent includes xylene, toluene, naphthalene, or any combinations thereof.
  • the hydrogenation may be performed at any suitable temperature to yield formation of the triblock copolymer. In certain embodiments, the hydrogenation may be performed at a temperature between 100°C and 125°C.
  • diazene used in the methods described herein may be obtained from any commercially available sources, or prepared according to any methods known in the art or any other suitable methods.
  • diazene may be produced by oxidation of hydrazine with hydrogen peroxide or air.
  • the decarboxylation of azodicarboxylic acid may also afford diazene.
  • Diazene may also be generated by elimination of sulfonohydrazides using a suitable base.
  • 2,4,6-triisopropylbenzenesulfonohydrazide may eliminate diazene upon treatment with sodium bicarbonate, a very mild base.
  • process 1000 depicts an exemplary reaction to produce diazene 110 by thermolysis of sulfonyl hydrazide 102 in the presence of tripropylamine (TPA) 104.
  • R w may be, for example, H or alkyl; and w may be 0, 1, 2, 3, 4 or 5.
  • Suitable examples of sulfonyl hydrazides include p-toluenesulfonyl hydrazide (TSH). It should be understood that TPA is a proton scavenger in process 1000, and other suitable proton scavengers may be used.
  • the ratio of TSH 102 to TPA 104 used may also vary.
  • the sulfonyl hydrazide may have a concentration of less than 20 wt .
  • the methods described herein may reduce or minimize the side reactions that may occur.
  • one possible side reaction that may occur is diazene disproportionation, as depicted in exemplary process 1200.
  • Another possible side reaction that may occur is PDMS degradation, as depicted in exemplary process 1300.
  • the methods provided herein produces less than 35 wt , less than 30 wt , less than 25 wt , less than 20 wt , less than 15 wt , less than 10 wt , less than 5 wt , or less than 1 wt% of polydialkylsiloxane degradants.
  • Such degradants may include, for example, poly(dimethylsiloxane) dihydroxyl terminated, poly(dimethylsiloxane) diamino terminated, poly(dimethylsiloxane) di (tert-butyl ) terminated, poly(dimethylsiloxane) dinitrile terminated, poly(dimethylsiloxane) dihydride terminated, and the degradants have a structure of formula (X) as described above.
  • BDB copolymer 120 used in process 1100 of FIG. 1 may be obtained from any commercially available sources, or prepared according to any methods known in the art or any other suitable methods.
  • FIG. 2 describes an exemplary reaction to produce the BDB copolymer.
  • anionic polymerization of 1,3-butadiene 204 may be initiated by sec-BuLi 202 in a solvent, such as cyclohexane, at 50 °C to yield 1,4-polybutadiene (PBD) 220.
  • a solvent such as cyclohexane
  • the anionic ring opening polymerization (ROP) of D 3 may be carried out using a two- step method.
  • hexamethyl(cyclotrisiloxane) monomer (D 3 monomer) 230 may be reacted with living PBD anions of polymer 220. This is the initiation step and approximately one D 3 monomer is added to each living chain.
  • a promoter such as tetrahydrofuran 232, may be added to the reaction mixture to give a cyclohexane/tetrahydrofuran mixture. This results in propagation.
  • Temperature may be controlled to reduce side reactions, including for example, backbiting and reshuffling reactions. This allows for control over the propagation reaction at high conversion of the monomer.
  • BDB triblock copolymer 250 may be produced by coupling the living poly(l,4-butadiene)-b-polydimethylsiloxanyl lithium polymer chains 240 with l,2-bis-(dimethylhalosilyl)ethane 242 and chlorotrimethylsilane 244.
  • poly(C t alkylene-b-dialkylsiloxane-b-C t alkylene) triblock copolymers produced according to any of the methods described herein.
  • poly(alkylene-b-dialkylsiloxane-b- alkylene) triblock copolymers by: combining poly(C t alkylene-b-dialkylsiloxane-b-C t alkylene) triblock copolymer and a polydialkylsiloxane homopolymer to produce a copolymer blend; and washing the copolymer blend to remove at least a portion of the polydialkylsiloxane homopolymer in the copolymer blend.
  • the poly(Ct alkylene-b-dialkylsiloxane-b-C t alkylene) triblock copolymer is a
  • the poly(Ct alkylene-b-dialkylsiloxane-b-C t alkylene) triblock copolymer is a
  • membranes made up of poly(alkylene-b-dialkylsiloxane-b- alkylene) triblock copolymers.
  • a membrane is a selective barrier that allows the passage of certain components and retains other components found in a feed solution. It should be understood that the influent of a membrane is generally referred to as the feed-stream; the liquid that passes through the membrane is generally referred to as the permeate; and the liquid containing the retained components is generally referred to as the retentate or concentrate.
  • each individual EDE triblock copolymer 302 contains a first polyethylene (PE) block 304, a polydimethylsiloxane (PDMS) block 306, and a second PE block 308.
  • PE polyethylene
  • PDMS polydimethylsiloxane
  • step 310 a plurality of EDE triblock copolymers aggregate based on hydrophobicity of the blocks to form an EDE triblock copolymer membrane.
  • the membrane contains a first microphase 312 of relatively hydrophobic PE blocks, a microphase 314 of relatively hydrophilic PDMS blocks, and a second microphase 316 of relatively hydrophobic PE blocks.
  • the PDMS microphase 314 forms the transporting phase of the membrane.
  • the transporting phase contains free volume 318, which is the free volume associated with the volume fraction of PDMS ( >DMS) present in the entire copolymer membrane.
  • FIG. 17 depicts a membrane with one PDMS-rich microphase and two PE-rich microphases, membranes as described herein may contain a plurality of PDMS- rich microphase and plurality larger than two of PE-rich microphases.
  • Synthetic membranes may be described based on their morphology.
  • Three exemplary types of synthetic membranes include: dense membranes (such as the poly(alkylene- b-dialkylsiloxane-b-alkylene) triblock copolymers), porous membranes (which may be used as support membranes), and asymmetric membranes (which is a combination thereof, and also referred to herein as supported membranes).
  • Dense and porous membranes are generally distinct from each other based on the size of separated molecules.
  • Dense membrane is usually a thin layer of dense material utilized in the separation processes of small molecules (usually in gas or liquid phase). Dense membranes may be for gas separations and reverse osmosis applications. Examples of dense membranes includes the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein.
  • Porous membranes are typically used in, for example, microfiltration, ultrafiltration, and dialysis applications.
  • the pores of a porous membrane may be a random network of the unevenly shaped structures of different sizes.
  • the formation of a pore can be induced by the dissolution of a "better” solvent into a “poorer” solvent in a polymer solution.
  • Other types of pore structure can be produced by stretching of crystalline structure polymers.
  • the structure of porous membrane is related to the characteristics of the interacting polymer and solvent, components concentration, molecular weight, temperature, and storing time in solution.
  • the thicker porous membranes may, in certain embodiments, provide support for the thin dense membrane layers, forming the asymmetric membrane structures. The latter are usually produced by a lamination of dense and porous membranes.
  • the membrane may be a free-standing membrane made up of any of the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein.
  • a free-standing membrane is unsupported, in contrast to the support membranes described below.
  • the membrane may be a supported membrane.
  • a supported membrane refers to a membrane made up of any of the poly(alkylene-b-dialkylsiloxane-b- alkylene) triblock copolymers described herein, and a porous support.
  • the porous support may be the porous membranes described above.
  • the porous membrane is a reverse osmosis membrane, a nanofiltration membrane, or ultrafiltration membrane.
  • the porous membrane includes polysulfone, polyacrylonitrile, polyvinylidene fluoride, or any combinations thereof.
  • the membranes described herein may have one or more of the following properties.
  • the membrane has an average thickness of at least 1 ⁇ ; or between 10 ⁇ and 200 ⁇ , between 1 ⁇ and 100 ⁇ , between 1 ⁇ and 50 ⁇ , or between 10 ⁇ and 20 ⁇ .
  • the thickness of a membrane may be measured according to any suitable methods known in the art.
  • the supported membranes include a selective layer (referring to the dense membrane layer) and a porous layer (which is a non- selective layer, and is referred to as the support layer).
  • the supported membrane has an average total thickness of less than 15 ⁇ . In other embodiments where the average thickness of the selective layer is less than 5 ⁇ , the average thickness of the porous layer in the supported membrane is less than 10 ⁇ .
  • the membrane has an ethanol permeability, normalized with the volume fraction of the transporting phase, between 7 mol m/m 2 s Pa and 14 mol m/m 2 s Pa.
  • membranes made up of a blend of polymers, such as any of the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein and a polydialkylsiloxane homopolymer.
  • Such membranes may be produced according to any suitable methods in the art.
  • a single EDE triblock copolymer 402 contains a first polyethylene (PE) block 404, a polydimethylsiloxane (PDMS) block 406, and a second PE block 408.
  • PE polyethylene
  • PDMS polydimethylsiloxane
  • a plurality of EDE triblock copolymers are combined with a plurality of PDMS homopolymers 410 in step 420.
  • the PE blocks are immiscible with the PDMS blocks and PDMS homopolymers, and the polymer mixture aggregates to form a membrane containing a first microphase 422 and a second microphase 426 comprising PE blocks, and a microphase 314 comprising PDMS.
  • the microphase 314 is the transporting phase of the membrane, and is composed of PDMS blocks 406 and PDMS homopolymers 430. It should be understood that while FIG. 18 depicts a membrane with one PDMS-rich microphase and two PE-rich microphases, membranes as described herein may contain a plurality of PDMS- rich microphase and plurality of PE-rich microphases.
  • the membrane may have one or more of the following properties.
  • the membranes made up of a blend of polymers have an average thickness between 5 ⁇ and 40 ⁇ .
  • the membranes made up of a blend of polymers have a volume fraction of the polydialkylsiloxane homopolymer in the transporting phase of between 0.01 and 0.2.
  • the membranes made up of a blend of polymers may further include a porous support.
  • the porous support may be a porous membrane.
  • the porous membrane is a reverse osmosis membrane, a nanofiltration membrane, or an ultrafiltration membrane.
  • the porous membrane includes polysulfone, polyacrylonitrile, polyvinylidene fluoride, or any combinations thereof.
  • membranes made up of poly(alkylene-b-dialkylsiloxane-b- alkylene) triblock copolymers, wherein the membranes have artificial free volume.
  • the membranes with artificial free volume are made up of a blend of polymers, such as any of the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer described herein and a polydialkylsiloxane homopolymer.
  • the artificial free volume is theoretical artificial free volume (/ADD), while in other embodiments, the artificial free volume is actual artificial free volume (/AFV)- Theoretical artificial free volume (/ADD) is the volume fraction of the one or more PDMS microphases occupied by PDMS homopolymer in the blend of polymers, assuming all of the homopolymer resides within the one or more microphasess.
  • Actual artificial free volume (/AFV) is the void in the one or more PDMS microphases left by PDMS homopolymer which has been removed.
  • a triblock copolymer membrane with actual artificial free volume may be produced by: combining any of the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein with a polydialkylsiloxane homopolymer to produce a copolymer blend; forming a copolymer blend membrane; and washing the copolymer blend membrane to remove at least a portion of the polydialkylsiloxane homopolymer in the copolymer blend membrane.
  • a single EDE triblock copolymer 402 contains a first polyethylene (PE) block 404, a polydimethylsiloxane (PDMS) block 406, and a second PE block 408.
  • PE polyethylene
  • PDMS polydimethylsiloxane
  • a plurality of EDE triblock copolymers are combined with a plurality of PDMS homopolymers 410 in step 420.
  • the PE blocks are immiscible with the PDMS blocks and PDMS homopolymers, and the polymer mixture aggregates to form a membrane containing a first microphase 422 and a second microphase 426 comprising PE blocks, and a microphase 314 comprising PDMS.
  • the microphase 314 is the transporting phase of the membrane, and is composed of PDMS blocks 406 and PDMS homopolymers 430.
  • the free volume 428 in the transporting phase is the free volume associated with the volume fraction of the PDMS block ( PDMS) present in the entire copolymer membrane.
  • the volume fraction of the PDMS microphase occupied by PDMS homopolymer 430 is /ADD- This is the theoretical artificial free volume that may be introduced by removal of the PDMS
  • step 440 the PDMS homopolymer 430 is removed by dissolution in solvent, producing a membrane comprised of EDE triblock copolymer with transporting phase 444.
  • FIG. 19 depicts exemplary process 500 to produce an EDE triblock copolymer membrane with artificial free volume.
  • EDE triblock copolymers are prepared containing polyethylene (PE) blocks separated by one polydimethylsiloxane (PDMS) block.
  • PDMS homopolymers are prepared.
  • the EDE triblock copolymers and the PDMS homopolymers are combined in 506 with a solvent that can at least partially solubilize both polymers.
  • the solution of two polymers is cast on a support in 508.
  • the PE blocks are immiscible with the PDMS blocks and PDMS homopolymers, and in step 510 the polymers aggregate to form a membrane with PE-rich microphases and PDMS-rich microphases. At least a portion of the PDMS-rich microphases form a transporting phase.
  • the membrane is dried and annealed at an elevated temperature in step 512.
  • the annealed membrane is washed with a solvent that solubilizes PDMS well, but solubilizes PE poorly.
  • This washing step removes the PDMS homopolymer from the PDSM-rich microphases without removing EDE triblock polymer.
  • the PDMS-rich microphases phases do not contain PDMS homopolymer, but still contains the PDMS block of the EDE triblock
  • the void left by the removed PDMS homopolymer is the actual artificial free volume (AFV) introduced into the produced EDE triblock copolymer membrane 518.
  • the membrane with artificial free volume is a free-standing membrane made up of any of the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein.
  • a free-standing membrane is unsupported, in contrast to the support membranes described below.
  • the membrane with artificial free volume is a supported membrane.
  • a supported membrane refers to a membrane made up of any of the poly(alkylene- b-dialkylsiloxane-b-alkylene) triblock copolymers described herein, and a porous support.
  • the porous support may be the porous membranes described above.
  • the porous membrane is a reverse osmosis membrane, a nanofiltration membrane, or ultrafiltration membrane.
  • the porous membrane includes polysulfone, polyacrylonitrile, polyvinylidene fluoride, or any combinations thereof.
  • membranes made up of poly(alkylene-b- dialkylsiloxane-b-alkylene) triblock copolymers with artificial free volume may have any of the one or more properties as described above for the membranes made up of poly(alkylene-b- dialkylsiloxane-b-alkylene) triblock copolymers.
  • the membrane with artificial free volume has an average thickness of at least 1 ⁇ ; or between 10 ⁇ and 200 ⁇ , between 1 ⁇ and 100 ⁇ , between 1 ⁇ and 50 ⁇ , or between 10 ⁇ and 20 ⁇ .
  • the supported membranes with artificial free volume include a selective layer (referring to the dense membrane layer) and a porous layer (which is a nonselective layer, and is referred to as the support layer).
  • the supported membrane has an average total thickness of less than 15 ⁇ . In other embodiments where the average thickness of the selective layer is less than 5 ⁇ , the average thickness of the porous layer in the supported membrane is less than 10 ⁇ .
  • the membrane with artificial free volume has a
  • polydialkylsiloxane block volume fraction (PDMS) of between 0.2 and 0.95, between 0.4 and 0.9, between 0.6 and 0.9, or between 0.7 and 0.8.
  • the membrane with actual artificial free volume has an actual artificial free volume (/AFV) of between 0.02 and 0.5, between 0.05 and 0.45, between 0.05 and 0.3, between 0.02 and 0.35, between 0.1 and 0.35, or between 0.15 and 0.2.
  • the membrane with actual artificial free volume has a polydialkylsiloxane block volume fraction ( to M s) of between 0.2 and 0.95, between 0.4 and 0.9, between 0.6 and 0.9, or between 0.7 and 0.8; and an actual artificial free volume ( AFV) of between 0.05 and 0.4, between 0.05 and 0.3, between 0.1 and 0.35, or between 0.15 and 0.2.
  • the membrane with theoretical artificial free volume has a theoretical artificial free volume (/ADD) of between 0.02 and 0.91, between 0.05 and 0.8, between 0.05 and 0.7, between 0.05 and 0.6, between 0.15 and 0.6, between 0.3 and 0.5, between 0.02 and 0.35, between 0.1 and 0.35, or between 0.15 and 0.2.
  • /ADD theoretical artificial free volume
  • the membrane with theoretical artificial free volume has a polydialkylsiloxane block volume fraction ( ⁇ DMS) of between 0.2 and 0.95, between 0.4 and 0.9, between 0.6 and 0.9, or between 0.7 and 0.8; and a theoretical artificial free volume (/ADD) of between 0.05 and 0.91, between 0.05 and 0.8, between 0.05 and 0.7, between 0.05 and 0.6, between 0.15 and 0.6, between 0.3 and 0.5, between 0.05 and 0.3, between 0.1 and 0.35, or between 0.15 and 0.2.
  • ⁇ DMS polydialkylsiloxane block volume fraction
  • /ADD theoretical artificial free volume
  • the actual or theoretical artificial free volume can be determined by comparing the total free volume of a membrane with the total free volume of a non-artificial free volume membrane, using relative transport and positron annihilation spectroscopy (PALS), or Xenon NMR or X-ray scattering (depending on the size of the voids).
  • PALS positron annihilation spectroscopy
  • Xenon NMR X-ray scattering
  • the membrane has a non-equilibrium free volume.
  • the non- equilibrium free volume of a membrane is the difference between the total free volume measured before annealing the membrane and the total free volume measured after annealing the membrane.
  • the membrane has a none-equilibrium free volume of between 0.05 and 0.5, between 0.05 and 0.4, between 0.05 and 0.3, between 0.1 and 0.35, or between 0.15 and 0.2.
  • the membrane has a free volume between 0.01 and 0.2.
  • Free volume may also be referred to as "void volume” or "pore size”. It should be understood that domain spacing may be affected by the presence of voids when the polydialkylsiloxane homopolymer, such as the PDMS homopolymer, is removed. Both the pore-free and pore- containing membranes may have similar volume fractions, but the domain spacing and transport properties may be different for a given thickness of membrane.
  • Free volume refers to different types of volume in the one or more polymer membranes described herein, including, for example, membranes containing EDE triblock copolymers; membranes containing triblock copolymer blends; and membranes with artificial free volume.
  • the free volume of membrane 320 made from EDE triblock copolymers is the free volume associated with the volume fraction of PDMS ( toMs) present in the entire copolymer membrane.
  • Membranes containing triblock copolymer blends also have different types of free volume.
  • the exemplary membrane produced by step 420 is composed of a blend of EDE triblock copolymers and PDMS homopolymers.
  • Membranes composed of triblock copolymers from which homopolymers have been removed also have different types of free volume.
  • the exemplary membrane produced by step 440 is composed of a blend of EDE triblock copolymers from which PDMS homopolymers were removed.
  • the types of free volume of this membrane include the free volume associated with the volume fraction of the PDMS block ( ⁇ DMS) present in the entire copolymer membrane; the volume introduced into the membrane by the removal of the PDMS homopolymers, also referred to as "actual artificial free volume” (AFV); and the combination of the free volume associated with the volume fraction of the PDMS blocks ( ⁇ DMS) present in the entire copolymer membrane, and the actual artificial free volume.
  • the actual artificial free volume is the free volume of the membrane in addition to the free volume associated with the volume fraction of the PDMS block ( ⁇ DMS) present in the entire copolymer membrane.
  • the membrane has a free volume of between 0.2 and 0.95, wherein the free volume refers to the free volume associated with the volume fraction of the PDMS blocks ( PDMS).
  • the membrane has a free volume of between 0.2 and 0.92, wherein free volume is the theoretical artificial free volume.
  • membrane has a free volume of between 0.2 and 0.95, wherein free volume is the total theoretical free volume.
  • the membrane has a free volume of between 0.1 and 0.4, wherein free volume is the actual artificial free volume.
  • the membrane has a free volume of between 0.2 and 0.95, wherein the free volume is the total actual free volume.
  • free volume (more specifically the actual artificial free volume) may be the volume fraction of polydialkylsiloxane homopolymer, such as PDMS homopolymer, that was in the block copolymer, and may be defined as the percentage ( ) of total volume.
  • the total free volume of a membrane is the summation of all the types of free volume (e.g. , "void volume” or "pore size") present in that membrane.
  • the total free volume of a membrane is the free volume associated with the volume fraction of the PDMS blocks (PDMS) present in the entire copolymer membrane.
  • the total free volume is the total actual free volume.
  • the total free volume of a membrane described herein is between 0.2 and 0.95, between 0.2 and 0.8, between 0.3 and 0.7, between 0.35 and 0.65, or between 0.35 and 0.45.
  • Free volume may be measured by looking at relative transport and positron annihilation spectroscopy (PALS), or Xenon NMR or X-ray scattering (depending on the size of the voids).
  • separating one or more organic compounds from an aqueous mixture of organic compounds involve contacting the aqueous mixture with any of the membranes described herein, including any membranes made up the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein, to separate one or more organic compounds from the aqueous mixture, and one or more of the organic compounds in the aqueous mixture selectively permeates through the membrane.
  • the copolymer compositions described herein may be hydrophobic to hinder the permeation of water molecules. Additionally, the copolymer compositions described herein contain a structural block that imparts essential mechanical properties to the membrane (e.g., polyalkylene) and an alcohol transporting block (e.g., polydialkylsiloxane).
  • a structural block that imparts essential mechanical properties to the membrane e.g., polyalkylene
  • an alcohol transporting block e.g., polydialkylsiloxane
  • the methods disclosed herein separate the one or more organic compounds from an aqueous solution produced in a fermentation process.
  • the separation is carried out using pervaporation techniques known in the art and described herein.
  • the one or more organic compounds include acetic acid, formic acid, levulinic acid, succinic acid, furfural, 5-hydroxymethylfurfural, 2-furoic acid, vanillic acid, ferulic acid, p-coumaric acid, syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid), 4-hydroxybenzoic acid; protocatechuic acid (3,4-dihydroxybenzoic acid); homovanillic acid (2-(4-hydroxy-3-methoxy-phenyl)acetic acid); caffeic acid (3,4-dihydroxycinnamic acid); sinapic acid; propionic acid; vanillylmandelic acid; 4-hydroxymandelic acid; 4- hydroxyphenylacetic acid; 3-hydroxybenzoic acid; 2,5-dihydroxybenzoic acid; benzoic acid; vanillin; syringaldehyde; 4-hydroxybenzaldehyde; coniferyl aldehyde (4-OH-3
  • protocatechualdehyde (3,4-dihydroxybenzaldehyde); acetovanillone (4'-hydroxy-3'- methoxyacetophenone); acetosyringone (3',5'-dimethoxy-4'-hydroxyacetophenone); guaiacol; coniferyl alcohol (4-(3-hydroxy-l-propenyl)-2-methoxyphenol); hydroquinone; catechol (pyrocatechol); vanillyl alcohol (4-hydroxy-3-methoxybenzyl alcohol); eugenol; or any mixture or combination thereof.
  • the one or more organic compounds include acetic acid, formic acid, levulinic acid, succinic acid, furfural, 5-hydroxymethylfurfural, or any mixture or combination thereof. In one embodiment, the one or more organic compounds is 5- hydroxymethylfurfural. In another embodiment, the one or more organic compounds include furfural. [0186] In some embodiments, the one or more organic compounds include one or more alcohols, such as, for example, ethanol, butanol, or any combination thereof. In certain embodiments, the one or more organic compounds include one or more C2-10 alcohols.
  • the one or more organic compounds separated include ethanol, w-butanol, isobutanol, 2-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, or 1-decanol, or any combination thereof.
  • the one or more organic compounds include acetone. In other embodiments, the one or more organic compounds include acetone, ethanol, and w-butanol produced in an acetone-ethanol-w-butanol (ABE) fermentation process. In other embodiments, the one or more organic compounds include one or more byproducts produced in a fermentation process. In some embodiments, the one or more organic compounds that are suitable for such separation processes are hydrophobic so they are able to permeate through the membrane and have a boiling point in the range that is suitable for pervaporation.
  • the one or more organic compound may be obtained from a renewable or biological source.
  • the membrane used to separate such one or more compounds may, in certain embodiments, have a separation factor (M SF ) between 1.0 to 4.0.
  • the method to separate the one or more organic compounds may be performed at a temperature of at least 100°C.
  • the membrane used to separate the one or more organic compounds has a ratio of the permeability of the one or more organic compounds to the permeability of water of between 1.0 and 4.0, between 2.0 and 4.0, or between 3.0 and 4.0. In some variations, the membrane used to separate the one or more organic compounds has a ratio of the permeability of butanol to the permeability of water of between 1.0 and 4.0, between 2.0 and 4.0, or between 3.0 and 4.0. In some embodiments, the method to separate the one or more organic compounds may be performed at a temperature of at least 100°C.
  • organic compounds produced according to any one of the methods described herein.
  • Such one or more organic compounds may be selected from the group consisting of acetone, ethanol, w-butanol, isobutanol, 2-butanol, 1-pentanol, 1- hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, acetic acid, formic acid, levulinic acid, succinic acid, furfural, 5-hydroxymethylfurfural, 2-furoic acid, vanillic acid, ferulic acid, p- coumaric acid, syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid), 4-hydroxybenzoic acid, protocatechuic acid (3,4-dihydroxybenzoic acid), homovanillic acid (2-(4-hydroxy-3-methoxy- phenyl)acetic acid), caffeic acid (3,4-dihydroxycin
  • a poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer comprising a polydialkylsiloxane block and polyalkylene end blocks, wherein the triblock copolymer has a molecular weight of at least 110 kg/mol, and wherein the polyalkylene is optionally substituted with halo.
  • polydialkylsiloxane is polydimethylsiloxane.
  • X is a polymeric block comprising one or more monomeric units independently having a structure of formula (M x ):
  • Y is a polymeric block comprising one or more monomeric units independently having a structure of formula (M y ):
  • Z is a polymeric block comprising one or more monomeric units independently having the structure of formula (M z ):
  • each R , R , R , R , R and R is independently H, halo, aliphatic or
  • the poly(Ct alkylene-b-dialkylsiloxane-b-C t alkylene) triblock copolymer is a poly(ethylene-b-dialkylsiloxane-b-ethylene) triblock copolymer
  • the poly(C 2 t alkadiene-b-dialkylsiloxane-b-C 2t alkadiene) is a poly(butadiene-b- dialkylsiloxane-b-butadiene) triblock copolymer.
  • a poly(C t alkylene-b-dialkylsiloxane-b-C t alkylene) triblock copolymer produced according to the method of any one of embodiments 8 to 21.
  • a membrane comprising a poly(C t alkylene-b-dialkylsiloxane-b-C t alkylene) triblock copolymer, wherein the membrane has one or more of the following properties (i) to (iv):
  • a membrane comprising: a poly(C t alkylene-b-dialkylsiloxane-b-C t alkylene) triblock copolymer of any one of claims 1 to 7 and 22; and a polydialkylsiloxane homopolymer.
  • a membrane comprising:
  • a polymer membrane comprising a poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer according to any one of embodiments 1 to 7 and 22, or a membrane of any one of embodiments 23 to 27;
  • the membrane of embodiment 28, wherein the porous support is a reverse osmosis membrane, a nanofiltration membrane, or an ultrafiltration membrane.
  • the membrane of embodiment 28 or 29, wherein the porous support comprises polysulfone, polyacrylonitrile, polyvinylidene fluoride, or any combinations thereof.
  • a method of separating one or more organic compounds from an aqueous mixture of organic compounds comprising contacting the aqueous mixture with a membrane to separate one or more organic compounds from the aqueous mixture, wherein (i) the membrane comprises a poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer according to any one of embodiments 1 to 7 and 22, or (ii) the membrane is a membrane according to any one of embodiments 23 to 31 ; and wherein one or more of the organic compounds in the aqueous mixture selectively permeates through the membrane.
  • a membrane comprising a plurality of poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers, wherein each triblock copolymer comprises a first polyalkylene end block and a second polyalkylene end block separated by a polydialkylsiloxane block; and wherein at least a portion of the plurality of triblock copolymers is aggregated to form one or more polyalkylene-rich microphases and one or more polydialkylsiloxane- rich microphases.
  • 41. The membrane of embodiment 40, wherein the membrane has one or more of the following properties (i) to (vii):
  • ⁇ DMS polydialkylsiloxane block volume fraction
  • PDMS polydialkylsiloxane block volume fraction
  • AFV actual artificial free volume
  • a membrane comprising a plurality of poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers and a plurality of polydialkylsiloxane homopolymers, wherein each triblock copolymer comprises a first polyalkylene end block and a second polyalkylene end block separated by a polydialkylsiloxane block; wherein at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of polydialkylsiloxane homopolymers are aggregated to form one or more polyalkylene -rich microphases and one or more polydialkylsiloxane-rich microphases.
  • a supported membrane comprising
  • the supported membrane of embodiment 57, wherein the porous support is a reverse osmosis membrane, a nanofiltration membrane, or an ultrafiltration membrane.
  • the supported membrane of embodiment 57 or 58, wherein the porous support comprises polysulfone, polyacrylonitrile, polyvinylidene fluoride, or any combinations thereof.
  • a method of separating one or more organic compounds from an aqueous mixture of organic compounds comprising contacting the aqueous mixture with a membrane to separate one or more organic compounds from the aqueous mixture, wherein the membrane is a membrane according to any one of embodiments 40 to 56, or a supported membrane according to any one of embodiments 57 to 60; and wherein one or more of the organic compounds in the aqueous mixture selectively permeates through the membrane.
  • the one or more organic compounds are selected from the group consisting of acetone, ethanol, w-butanol, isobutanol, 2-butanol, 1-pentanol, 1- hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, acetic acid, formic acid, levulinic acid, succinic acid, furfural, 5-hydroxymethylfurfural, 2-furoic acid, vanillic acid, ferulic acid, p- coumaric acid, syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid), 4-hydroxybenzoic acid, protocatechuic acid (3,4-dihydroxybenzoic acid), homovanillic acid (2-(4-hydroxy-3-methoxy- phenyl)acetic acid), caffeic acid (3,4-dihydroxycinnamic acid), sinapic acid, propionic acid, vaniUy
  • a method of producing a membrane comprising: providing a plurality of poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers; providing a plurality of polydialkylsiloxane homopolymers; combining the plurality of triblock copolymers, the plurality of homopolymers, and a first solvent to form a polymer mixture, wherein the first solvent solubilizes at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of homopolymers; and casting the polymer mixture to produce a membrane, wherein the membrane comprises at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of homopolymers.
  • a poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer comprising a polydialkylsiloxane block and polyalkylene end blocks, wherein the triblock copolymer has a molecular weight of at least 50 kg/mol, and wherein the polyalkylene is optionally substituted with halo.
  • 1,3-Butadiene (Aldrich, 99%) was purified by drying an appropriate amount of monomer over finely ground CaH 2 overnight, followed by distillation in activated molecular sieves where it remained in contact overnight. The butadiene was then vacuum-transferred to a reactor containing n-BuLi where it remained with continuous stirring at 0 °C for 1 hour. The resulting monomer was distilled in a reactor containing toluene that had been dried as described below. The monomer was stored at -20 °C in the glove box and was used within the period of 2 weeks.
  • Toluene was purified by passing through solvent purification columns followed by stirring overnight over finely ground CaH 2 . The toluene was then distilled and stored in a reactor over polystyryl lithium obtaining the characteristic red color.
  • THF was purified by passing through solvent purification columns followed by stirring overnight over finely ground CaH 2 and then stored in a reactor over a Na/benzophenone mixture obtaining the characteristic blue color.
  • Hexamethylcyclotrisiloxane, D 3 (Gelest, 95 %) was purified as follows: D 3 was melted by heating at 80 °C, put in a flask, diluted by an equal amount of purified cyclohexane, and stirred overnight over CaH 2 . Then the solvent along with the monomer was distilled into a flask containing polystyryl lithium. The monomer was in contact with polystyryl lithium for about 2 hours at room temperature and then it was distilled into a flame dried reactor along with the solvent by heating at 80 °C. Finally, the monomer was isolated by distilling cyclohexane to another reactor at room temperature.
  • n and dispersities, D of the BDB precursors were obtained using a Viscotek TDA 302 GPC system that has a guard column, a set of four Viscotek columns (300 mm x 7.8 mm, T-3000, T-4000, T-5000, and T-6000 columns) and a refractive index detector, with THF eluent (flow rate of 1 mL/min, 35 °C).
  • the instrument was calibrated with polystyrene standards (Agilent Easivials PS-M). The molecular weights of the poly(l,4-butadiene) precursors were calculated based on triple detection experiments.
  • polyethylene segments Spectra were analyzed to determine copolymer compositions as well as hydrogenation and degradation percentages.
  • TGA Thermogravimetric Analysis
  • DSC scans consisted of two heating/cooling cycles and were conducted over the range 0-150 °C at a rate of 10 °C/min.
  • the glass transition temperatures ( g ) for EDE32-335, presented here is from the inflection point of the transition in the second heating run.
  • the enthalpy of fusion of the first heating cycle was used in order to estimate the degree of crystallinity of polyethylene and the polyethylene phase in the EDE triblock copolymer samples by comparing it to the enthalpy of fusion of 100% crystalline polyethylene.
  • a value of 4.11 kJ per repeating unit was used to estimate the enthalpy of fusion of 100% crystalline polyethylene.
  • SAXS Small angle x-ray scattering
  • WAXS Wide angle x-ray scattering
  • PALS Positron Annihilation Lifetime Spectroscopy
  • fractional free volume was calculated assuming spherical free volume elements using the radius determined from the lifetime (R) and the associated Intensity (I 3 ):
  • FFV PALS C ⁇ nR 3 I 3 where C is an empirical constant determined to be approximately 0.0018 nm " .
  • the membranes were measured on an EG&G Ortec fast-fast coincidence system using 22 NaCl ( ⁇ 1.5 x 10 6 Bq) as the source of positrons which was sealed in a Mylar envelope.
  • the membranes were cut and stacked into 2 mm thick bundles and placed either side of the positron source.
  • the measurements were taken under vacuum (1 x 10 "5 torr) with a minimum of 5 files collected at 4.5 x 10 6 integrated counts per file for each membrane.
  • a source correction of 1.48 ns and 3.033% was subtracted from each spectra.
  • the spectra were deconvoluted using LT v.9 software.
  • BDB PBD-b-PDMS-b-PBD
  • This Example describes the synthesis of BDB triblock copolymers with varying molecular weights.
  • the BDB triblock copolymer was prepared by coupling the living poly(l,4-butadiene)-b-polydimethylsiloxanyl lithium polymer chains with 1,2-bis-
  • BDBX-Y The characteristics of the four BDB triblock copolymers used in this study are summarized in Table 1. Samples in the table are labeled as "BDBX-Y", where X is the number averaged molecular weight of the copolymer, and Y is the PDMS volume fraction. 1H NMR spectroscopy analysis of the final product was used to calculate the molar ratio between the polybutadiene and polydimethylsiloxane monomeric units. See FIG. 3A.
  • FIG. 3B shows GPC traces of a typical PBD precursor (prior to adding D3 monomer) and the BDB triblock copolymer obtained from the corresponding precursor. Both samples show predominantly one narrow GPC peak with clear shift toward higher molecular weights after the addition of the PDMS block and coupling.
  • the dispersity, D, of the BDBX-Y was 1.14 which suggests high selectivity toward the ring opening polymerization reaction at high conversion of the monomer under the conditions specified above.
  • the molecular weights of the BDB copolymers synthesized ranged from 119 to 335 kg/mol, PDMS volume fractions ranging from 0.23 to 0.78, and D ranging from 1.14 to 1.28 (see Table 1 above).
  • This Example describes the synthesis of EDE triblock copolymers with varying molecular weights.
  • TSH p-toluenesulfonyl hydrazide
  • BDB hydrogenation of BDB was performed, wherein diazene then donates two hydrogen atoms to each double bond of the PBD monomeric units.
  • reaction 2 in the reaction scheme above
  • reaction 2 was carried out in a 1L three-neck round bottom flask which was equipped with magnetic stirring, a reflux condenser, a thermometer and a stopper.
  • the apparatus was supplied with positive pressure of dry argon.
  • Predetermined amounts of BDB block copolymer and o-xylene were added, and the mixture was left to stir for 1 hour at 60 °C. This resulted in the complete dissolution of the polymer.
  • TPA tripropylamine
  • the addition of large excess of tripropylamine (TPA) as a proton scavenger was found to affect the efficacy of the hydrogenation.
  • the hydrogenation reaction mixture now contained two nucleophiles, the p-toluenesulfinate anion and the tripropylamine.
  • the susceptibility of the siloxane bond to TPA was tested by performing a blank reaction where the BDB precursor polymer was heated at 135 °C in the presence of only, the weakly nucleophilic TPA, for 4 hours (no TSH was present). In this case, 1H NMR and GPC analysis of the purified product showed no evidence of degradation.
  • Entry 1 shows 100% hydrogenation of PBD but in 91 % mol degradation of PDMS. Reducing the TSH and polymer concentration by a factor of four was observed to reduce the PDMS mol % degradation to 34 without affecting hydrogenation, indicating that decreasing the initial TSH concentration slows down the PDMS degradation reaction (reaction 4 in the reaction scheme above). Comparison of entries 3 and 2 indicates that reducing the reaction temperature to 115 °C also reduces degradation of PDMS without affecting the hydrogenation efficacy. Entry 3 indicates slowing down the rate at which diazene active species disproportionate (note that reaction 3 is second order to diazene concentration while reaction 2 is first order to diazene concentration). In entry 4 the reaction time is reduced from 240 to 180 minutes with all other conditions identical with those used in entry 3. Under these conditions, 0 % mol PDMS degradation and 100% PBD hydrogenation were observed.
  • EDEX-Y The characteristics of the final EDE copolymers are listed in Table 3 below. Samples are named EDEX-Y where X is the total molecular weight of the copolymer (kg/mol) and Y is the volume fraction of the PDMS block.
  • FIG. 7 shows SAXS profiles of the EDE membranes at room temperature.
  • the SAXS profiles were isotropic indicating that the membrane preparation process led to the formation of randomly oriented grains.
  • the scattering profile of the nearly symmetric copolymer, EDE209-45, is consistent with that expected from samples with lamellar
  • the scattering profiles of the other copolymers, EDE124-42, EDE187-22 and EDE340-77 contained primary scattering peaks only. The locations of the primary scattering peaks are indicated by filled triangles in FIG. 7.
  • FIG. 8 provides a plot of d versus M n , the total copolymer molecular weight. SAXS profiles collected at high temperatures, well above the melting temperature of the PE blocks (up to 160 °C), were not distinguishable from the room temperature profiles.
  • FIG. 14 shows thermogravimetric analysis (TGA) data of the purified product synthesized under the original and optimized conditions after purification by
  • the TGA results show in both cases two degradation regimes.
  • the mass loss between 410 °C and 430 °C is due to thermal degradation of the PE block whereas the mass loss observed from 440 to 580 °C is due to thermal degradation of PDMS.
  • the TGA results of entry 1 shows that 82 wt. % of the material degrades between 410 to 430 °C and about 18 wt. % of the total weight of the polymer is lost between 440 and 580 °C.
  • the product of entry 4 lost about 26 wt. % between 410 °C and 430 °C and 74 wt. % between 440-580 °C.
  • EDE340-77 the product of entry 4, was also analyzed by DSC. The presence of one endothermic peak at 102.2 °C was observed, which corresponds to the PE melting point; and an exothermic peak at 80.2 °C, which corresponds to the PE crystallization (see FIG. 15).
  • Free standing films could be readily formed by the synthesized EDE triblock copolymers with thicknesses as low as 15 nm by a simple solvent casting methodology. This thickness is significantly lower compared to films formed by polystyrene-b- polydimethylsiloxane-b-polystyrene, SDS, where the thinnest free standing films have been observed around 60 ⁇ . Analysis of these films by wide angle x-ray scattering (WAXS) revealed the presence of two Bragg peaks at 0.124 nm "1 and 0.139 nm "1 which is signature of the [110] and [200] planes of polyethylene crystalline domains (see FIG. 16).
  • WAXS wide angle x-ray scattering
  • This Example describes the preparation and use of EDE membranes.
  • EDE 150 mg was dissolved in cyclohexane (20 mL) and stirred at 65 °C for a minimum of 5 hours.
  • the warm solution was poured on a Teflon® sheet that was preheated at 70 °C and placed on a levelled surface.
  • a metal tube with smoothened edges was employed as a template.
  • the cast area was covered with aluminum foil to slow down solvent evaporation. After solvent removal (approximately 5 hours) the film was peeled off the surface and was used for further characterization.
  • FIGS. 9A and 9B show the dependence of ethanol (FIG. 9A) and water (FIG. 9B) permeabilities on PDMS volume fraction, PDMS .
  • Ethanol and water permeabilities were normalized with ( ⁇ ⁇ /$TM ⁇ 5 and Pw/$rans), which accounts for the different volume fraction of PDMS in each block copolymers.
  • FIG. 10 shows the dependence of membrane separation factor, ⁇ 3 ⁇ 4w, on r a ns- From these data, ⁇ 3 ⁇ 4w was not observed to be a strong function of morphology in this system.
  • the membrane separation factor for EDE membranes ranges from 0.75 to 0.98 for all the samples.
  • Permeability through a strongly microphase separated block copolymer can be expressed as: where 0 trans is the volume fraction of the transporting phase, P i o is the intrinsic permeability of the pure transporting phase, and /is a factor that accounts for the morphology of the microphase separated block copolymers, for permeability of water (W), ethanol (E), or butanol (B).
  • W water
  • E ethanol
  • B butanol
  • EDE/PDMS blends were prepared using a solvent casting methodology on heated stage to control film temperature. Solutions of EDE, PDMS, and cyclohexane were prepared at 70 °C onto a porous Teflon® substrate at a concentration of 0.05 g EDE per mL of cyclohexane. The resultant films, with thicknesses in the 5-40 ⁇ range, were dried in a vacuum oven, ⁇ PDMS is defined as the PDMS volume fraction in the supported membranes and thus ⁇ PDMS - PDMS, as the fraction of volume occupied by the PDMS homopolymer in the EDE/PDMS mixture.
  • a is defined as the ratio of the molecular weight of the PDMS homopolymer to that of the PDMS in the block copolymer (the former is 14 kg moF 1 ).
  • the same PDMS homopolymer is added regardless of a.
  • the polymers are named EDE XX-YY/ZZ where XX is the total average molecular weight of the copolymer, YY is the PDMS volume fraction, and ZZ is the additional PDMS volume fraction ( ⁇ PDMS- ⁇ PDMS) -
  • Table 4 shows the characteristics of supported membranes that were fabricated by blending EDE triblock copolymer with a PDMS homopolymer.
  • the supported membranes were then exposed to a number of washing cycles. First the supported membranes were immersed in THF to dissolve out PDMS homopolymer chains. Then, the membrane was immersed in methanol. Three such cycles were performed for each one of the supported membranes. In all cases, the difference in mass of the films, measured before and after washing and subsequent drying steps, was within experimental error of the mass of homopolymer PDMS added in the first step (+ 2%). By removal of the PDMS homopolymer from the EDE membrane the creation of extra free volume was achieved. The free volume was assumed to be equal with the volume that the PDMS homopolymer was occupying prior to dissolution ( ⁇ PDMS- ⁇ DMS)-
  • FIGS. 12A and 12B show ethanol (FIG. 12A) and butanol (FIG. 12B) normalized permeabilities as a function of r a ns -
  • the red circles indicate the permeability of the membranes exposed to three washing cycles.
  • the black triangles show the theoretical increase in ethanol and butanol permeability for increased PDMS volume fraction in the membrane (while the red circles show the effect of 'exchanging' the extra PDMS volume with free volume as measured by pervaporation experiments).
  • This Example demonstrates the preparation and characterization of a series of EDE membranes with artificial free volume.
  • EDE/PDMS blend polymer membranes were prepared following procedure similar to that described in Example 3. Briefly, solutions of EDE, PDMS, and cyclohexane (0.08 g EDE per mL of cyclohexane) were cast onto a porous Teflon® substrate at 70 °C. The resulting films had thicknesses in the 20-30 ⁇ range. They were dried in a vacuum oven for approximately 16 h at room temperature. This was followed by drying and annealing the films for 24 h at 130 °C. The blended membranes were immersed in THF for five minutes to dissolve out PDMS homopolymer chains. Then the membranes were immersed in methanol for 5 minutes.
  • Table 6 summarizes the characteristics of the polymer membranes.
  • the polymers are named EDE XX-YY/ZZ, where XX is the total average molecular weight of the copolymer, YY is the PDMS volume fraction percent in the pure block copolymer, and ZZ is the additional PDMS volume fraction percent (100 x
  • FIGS. 20A and 20B show background-corrected SAXS profiles for the two series of dried films that were studied.
  • Sample EDE129-41 exhibited a broad primary scattering peak superposed on a monotonically decreasing background, and no higher order peaks.
  • FIGS. 21 A and 21B show dark- field transmission electron microscopy (TEM) images of cryo-microtomed samples of membranes EDE129-41 and EDE129-41/17, respectively. Both samples exhibit a lamellar morphology with little long-range order, consistent with the SAXS data (FIG. 20A). The dark lamellae represent the polyethylene-rich microdomains, while the bright lamellae represent the PDMS-rich microdomains. The TEM images are also consistent with the absence of a mesoporous structure.
  • the free-volume content of the EDE129-41 series was analyzed directly by positron annihilation lifetime spectroscopy (PALS).
  • PALS positron annihilation lifetime spectroscopy
  • This technique enables determination of the size and relative concentration of free-volume elements by measuring the intensity (/ 3 ) and lifetime (3 ⁇ 4) of the ortho-positronium states (oPs).
  • a description of the technique and the approach used for analyzing PALS data may be found in Merkel TC, Freeman BD, Spontak RJ, He Z, Pinnau I, Meakan P, Hill AJ; Sorption, transport, and structural evidence for enhanced free volume in poly(4-methyl-2-pentyne)/fumed silica nanocomposite membranes, Chemistry of Materials (2003), 15, pages 109-123.
  • the spectra of the PALS signals from all of the tested samples were consistent with a linear sum of two exponential functions, indicating the presence of free- volume elements with two distinct sizes.
  • FIG. 22A shows results of PALS analysis for samples EDE129-41, EDE129-41/9 and EDE129-41/17.
  • the neat EDE129-41 sample exhibits two populations of free-volume elements centered around cavities with diameters of 0.4 and 0.8 nm.
  • the intensities at the peaks of the distributions corresponding to the small and large cavities are shown in FIGS. 22B and 22C, respectively.
  • the intensity corresponding to the larger cavities increases with increasing /ADD, while that corresponding to the smaller cavities decreases with increasing /ADD-
  • the larger cavities have the largest effect on the distribution functions shown in FIG. 22A.
  • the fractional free volume of EDE129-41 was found to be 13.9 %.
  • the EDE block copolymer contains two types of microdomains with different free-volume characteristics.
  • a polyethylene (PE) homopolymer was synthesized using the same protocol that was used for the synthesis of the triblock copolymers, and the free- volume of this homopolymer was measured by PALS. The / ; versus ⁇ 3 ⁇ 4 curve obtained is shown in FIG. 26.
  • the FFV of pure PE was determined to be 5.4 % .
  • the FFV of PDMS-rich microphases in the triblock membrane samples was estimated using the following equation:
  • the equation for FFVPDMS assumes that the PE-rich microphase in EDE contains the same fractional free volume as the PE homopolymer. Polyethylene is a semicrystalline polymer, and it is generally assumed that the free-volume elements reside primarily in the amorphous regions. The enthalpy of melting for each of the samples was measured using differential scanning calorimetry (DSC). The PE homopolymer, the neat EDE 129-41, and samples with artificial free- volume all showed percent crystallinities of about 28 %. Based on the equation for FFV PDMS above, the FFV of the PDMS-rich microphase in EDE129-41 is 26.7 %.
  • This Example demonstrates the use of a series of EDE membranes with artificial free volume in purifying two model mixtures relevant to biofuel production, butanol/water (1.5 wt. % butanol) and ethanol/water (8 wt. % ethanol) by pervaporation.
  • the EDE membranes used were prepared and characterized following the procedure as described in Example 4 above. Pervaporation experiments of ethanol/water and butanol/water mixtures were conducted on a laboratory bench test unit built by Sulzer Chemtech, Germany.
  • the membrane was held inside a circular cell restrained with an o-ring, providing a total
  • M[ is the mass of individual permeant
  • A is the permeation area (37 cm ) and ⁇ ⁇ is the permeate collection time.
  • B is butanol
  • W is water.
  • Membrane permeability, P ; was calculated from the following equation: where t is the membrane thickness, ⁇ ⁇ is the feed mole fraction, ⁇ ⁇ is the activity coefficient, ⁇ . ⁇ is the saturated vapor pressure, y t is the permeate mole fraction and p is the permeate pressure. Values of y i were determined by analyzing permeate samples by 1H NMR
  • the butanol, ethanol and water permeabilities (P B , P E and Pw) through the membranes can be expressed as: where $r ans accounts for the different volume fractions of PDMS-rich transporting phase that includes the theoretical volume fraction of the added homopolymer (/ ADD ) in each block copolymer, P ⁇ - 0 is the intrinsic permeability of the pure transporting phase, and m is a
  • FIG. 24 shows the dependence of P E , 0 (left y-axis) and P B , 0 (right y-axis) on / ADD (top x-axis).
  • the intrinsic butanol and ethanol permeabilities for the neat EDE samples thus obtained were
  • FIG. 27 As actual artificial free- volume / AFV is a linear function of added homopolymer volume fraction / ADD , the data in FIG. 27 can be used to investigate the dependence of permeability on artificial free- volume.
  • the bottom x-axis of FIG. 23 was used to quantify the effect of actual artificial free-volume on intrinsic butanol and ethanol permeabilities. Butanol and ethanol permeabilities through EDE129-41/9 and EDE129-41/17 were measured two months after the data shown in FIG. 23 were gathered. These permeabilities were within experimental error of those reported in FIG. 23. This demonstrates the stability of artificial free-volume created by block copolymer aggregation.
  • FIG. 24 The effect of artificial free-volume on selectivity is shown FIG. 24, where ⁇ 3 ⁇ 4 jW and ⁇ 3 ⁇ 4w are plotted versus /AFV-
  • the plot in FIG. 24 indicates that the enhancement in flux reported in FIG. 23 is not obtained at the expense of selectivity. In fact, selectivity increases slightly with increasing /AFV-
  • the data in FIG. 24 indicate that the actual artificial free-volume created by the self-assembly process is more hydrophobic than that present in cross-linked PDMS.
  • the dielectric constant of vacuum (8.85 x 10 "12 F/m) is lower than that of PDMS (2.2 x 10 "11 F/m).
  • this example demonstrates that it is possible to increase the size and concentration of free- volume cavities in a controlled fashion by block copolymer self-assembly.
  • membranes that are chemically similar to their precursors but contain systematically varied levels of free-volume.
  • the utility of these materials was demonstrated by testing membranes for butanol/water and ethanol/water mixtures, separations that require reverse selectivity and are relevant to biofuel production.
  • the presence of artificial free-volume resulted in increase of both butanol and ethanol permeabilities without adversely affecting selectivity.

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Abstract

Provided herein are poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers that may be suitable for membrane fabrication and/or pervaporation applications. Specifically, such triblock copolymers may be used in methods of separating one or more organic compounds from an aqueous solution using membranes derived from such triblock copolymers.

Description

POLY(ALKYLENE-fi-DIALKYLSILOXANE-fi-ALKYLENE) TRIBLOCK COPOLYMERS
AND USES THEREOF
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent Application No.
62/004,153 filed May 28, 2014, which is incorporated herein by reference in its entirety.
FIELD
[0002] The present disclosure relates to poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers and uses thereof, including the use of membranes made up of such triblock copolymers for separating organic compounds in an aqueous mixture.
BACKGROUND
[0003] Increasing concerns about global warming and decreasing amount of easily accessible oil reserves boosted the interest in biofuels in the last decade. The production of biofuels from renewable resources such as lignocellulosic feedstocks would allow production of fuel with no net carbon dioxide release to the atmosphere, therefore making biofuels an environmentally benign energy source. Biofuel production from lignocellulosic feedstocks includes degradation of feedstock to fermentable sugars, fermentation of the sugars, and separation of alcohol from the fermentation broth. Conventionally, a distillation process may be used to separate the alcohol from the fermentation broth at the end of the fermentation process, but such process requires intensive energy resources and also suffers from azeotrope formation. Pervaporation may also be used to separate biofuels from dilute aqueous solutions, and can serve as an alternative technique to distillation. Since the alcohol concentration in fermentation broth is typically low (<10%), pervaporation is more economical and practical to separate the alcohol from the other components of the fermentation broth (water, sugar, bacteria and others).
[0004] Pervaporation is a membrane separation technique that is utilized to separate liquid mixtures through a membrane via a solution-diffusion mechanism. First, permeation through the membrane takes place and then the permeate is collected as a vapor on the other side of the membrane. The evaporation of the permeate on the permeate side of the membrane creates the driving force for the transfer of the permeate. The pervaporation membrane behaves as a selective barrier between the feed and the permeate; therefore, the selection of the pervaporation membrane is crucial to achieve high selectivity and fluxes. The permeability of the components through the membrane is the multiplication of their diffusion and solubility in the membrane material. For instance, for pervaporation of alcohol-water mixtures, the diffusivity of water is greater than the diffusivity of the alcohol due to the smaller dimension of the water molecule. A membrane material with higher alcohol solubility may be useful to obtain high alcohol permselectivity.
[0005] Thus, there is a need for materials that are selective for certain alcohols and have mechanical properties suitable for membrane fabrication and/or pervaporation applications.
SUMMARY
[0006] Provided herein are poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers that are suitable for membrane fabrication and/or pervaporation applications.
[0007] In one aspect, provided is a poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer made up of a polydialkylsiloxane block and polyalkylene end blocks.
[0008] In another aspect, provided is a triblock copolymer having a structure of formula (I): x-Y-z (I), wherein:
X is a polymeric block comprising one or more monomeric units independently having a structure of formula (Mx):
Figure imgf000003_0001
Y is a polymeric block comprising one or more monomeric units independently having a structure of formula (My):
Figure imgf000003_0002
Z is a polymeric block comprising one or more monomeric units independently having the structure of formula (Mz):
Figure imgf000004_0001
each R , R , R , R , R and R is independently H, halo, aliphatic or
haloaliphatic.
It should be understood that X and Z are polymeric end blocks. Such end blocks may be the same or different. In certain embodiments, X and Z are the same, such that the triblock copolymer may have a structure of formula: X- Y-X or Z- Y-Z.
[0009] In some embodiments, the triblock copolymer has a molecular weight of at least 110 kg/mol. In certain embodiments, the triblock copolymer has a polydialkylsiloxane volume fraction between 0.2 and 0.95. In certain embodiments, the triblock copolymer has a
morphology capable of providing a continuous transporting phase. In certain embodiments, the triblock copolymer has a domain spacing (d) between 10 nm and 90 nm.
[0010] Provided are also compositions made up of the triblock copolymers described herein. In certain embodiments, the composition has less than 35 wt% of polydialkylsiloxane degradants.
[0011] Provided are also methods of producing the triblock copolymers described herein. In one aspect, provided is a method of producing a poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer, wherein t is an integer greater than or equal to 2. The method includes hydrogenating a poly(C2t alkadiene-b-dialkylsiloxane-b-C2t alkadiene) triblock copolymer in the presence of diazene to produce the poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer.
[0012] Provided are also membranes made up of the triblock copolymers described herein. In one aspect, provided is a membrane made up of a poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer. Such membrane may be suitable for separating renewable materials.
[0013] In other aspects, provided is a membrane made up of: (i) a poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer according to any of the embodiments described herein; and
(ii) a polydialkylsiloxane homopolymer.
[0014] In yet other aspects, provided is a membrane made up of:
(i) a polymer membrane made up of a poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer according to any of the embodiments described herein, or a polymer membrane made up of a poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer according to any of the embodiments described herein and a
polydialkylsiloxane homopolymer; and
(ii) a porous support.
[0015] In other aspects, provided is a membrane including a plurality of poly(alkylene-b- dialkylsiloxane-b-alkylene) triblock copolymers, wherein each triblock copolymer comprises a first polyalkylene end block and a second polyalkylene end block separated by a polydialkylsiloxane block; wherein at least a portion of the plurality of triblock copolymers is aggregated to form one or more polyalkylene-rich microphases and one or more polydialkylsiloxane- rich microphases;
[0016] In some aspects, the membrane has an actual artificial free volume of between 0.02 and 0.45. In some aspects, the membrane has a ratio of the permeability of one or more organic compounds to the permeability of water of between 1.0 to 4.0. In other aspects, the membrane further includes one or more polydialkylsiloxane homopolymers.
[0017] In other aspects, provided is a membrane with a non-equilibrium free volume, wherein the non-equilibrium free volume is the difference in total free volume measured before annealing and the total free volume measured after annealing.
[0018] In still other apsects, provided is a membrane including a plurality of poly(alkylene- b-dialkylsiloxane-b-alkylene) triblock copolymers and a plurality of polydialkylsiloxane homopolymers, wherein each triblock copolymer comprises a first polyalkylene end block and a second polyalkylene end block separated by a polydialkylsiloxane block; wherein at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of polydialkylsiloxane homopolymers are aggregated to form one or more polyalkylene -rich microphases and one or more polydialkylsiloxane-rich microphases.
[0019] In another aspect, provided herein is a method of producing a membrane by: providing a plurality of poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers; providing a plurality of polydialkylsiloxane homopolymers; combining the plurality of triblock copolymers, the plurality of homopolymers, and a first solvent to form a polymer mixture, wherein the first solvent solubilizes at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of homopolymers; and casting the polymer mixture to produce a membrane, wherein the membrane comprises at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of homopolymers.
[0020] In some aspects, the method further includes contacting the membrane with a second solvent, wherein the second solvent solubilizes at least a portion of the plurality of
homopolymers; and removing at least a portion of the solubilized homopolymers.
[0021] A poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer comprising a polydialkylsiloxane block and polyalkylene end blocks, wherein the triblock copolymer has a molecular weight of at least 50 kg/mol, and wherein the polyalkylene is optionally substituted with halo.
[0022] In yet another aspect, provided is a method of separating one or more organic compounds from an aqueous mixture of organic compounds. The method includes contacting the aqueous mixture with a membrane to separate one or more organic compounds from the aqueous mixture, wherein one or more of the organic compounds in the aqueous mixture selectively permeates through the membrane. In some aspects, the one or more organic compounds are obtained from a renewable or biological source. In certain aspects, the ratio of the permeability of the one or more organic compounds to the permeability of water is between
1.0 to 4.0. The membrane may be according to any of the embodiments described herein.
[0023] Provided is also one or more organic compounds, such as alcohols, separated according to any of the methods described herein.
DESCRIPTION OF THE FIGURES
[0024] The present application can be understood by reference to the following description taken in conjunction with the accompanying figures, in which like parts may be referred to by like numerals.
[0025] FIG. 1 refers to an exemplary reaction scheme for synthesis of poly(ethylene-b- dimethylsiloxane-b-ethylene) (EDE) triblock copolymers via hydrogenation of poly(l,4- butadiene)-b-polydimethylsiloxane-b-poly(l,4-butadiene) (BDB) using diazene produced via thermolysis of p-toluenesulfonyl hydrazide. FIG. 1 also depicts possible side reactions that may occur based on the starting materials used to synthesize the EDE triblock copolymer.
[0026] FIG. 2 refers to an exemplary reaction scheme for synthesis of BDB triblock copolymers via sequential anionic polymerization of 1,3-butadiene and
hexamethycyclotrisiloxane and subsequent coupling with l,2-bis(dimethylchlorosilyl)ethane.
[0027] FIG. 3A is an exemplary 1H NMR spectrum of triblock copolymer, BDB335-78 (500 MHz, CDC13).
[0028] FIG. 3B depicts an exemplary gel permeation chromatograph of PBD32
homopolymer (dashed line) and exemplary BDB335-78 triblock copolymer (solid line).
[0029] FIG. 4 is an exemplary gel permeation chromatograph of commercially available PDMS homopolymer before and after exposing it to the hydrogenation conditions of Study 2 in Example 2.
[0030] FIG. 5 depicts an exemplary 1H NMR spectra of hydrogenation products for various reaction conditions described in Table 2 of Example 2 for BDB335-78 (500 MHz, 353 K, d toluene). [0031] FIGS. 6A, 6B, and 6C are exemplary high temperature gel permeation chromatographs of BDB335-78. FIG. 6A is before hydrogenation (dashed line) and after hydrogenation under standard conditions (solid line) (entry 1, Table 2 of Example 2). FIG. 6B is before hydrogenation (dashed line) and after hydrogenation under optimized conditions (solid line) (entry 4, Table 2 of Example 2). FIG. 6C is final product under the hydrogenation conditions of entry 6 without additional purification (entry 6, Table 2 of Example 2).
[0032] FIG. 7 depicts exemplary SAXS profiles of microphase separated EDE triblock copolymers collected at 25 °C, wherein scattering intensity is plotted as a function of the magnitude of the scattering vector, q, and filled triangles represent the primary scattering peaks and the open triangles represent the higher order scattering peaks.
[0033] FIG. 8 depicts an exemplary graph comparing domain spacing versus total number average block copolymer molecular weight; scaling law d~Mn 0'67 is represented by the solid line.
[0034] FIGS. 9A and 9B depict exemplary graphs for ethanol (FIG. 9A) and water (FIG. 9B) permeabilities normalized by PDMS volume fraction as a function of PDMS volume fraction.
[0035] FIG. 10 depicts an exemplary graph showing ethanol/water selectivity as a function of PDMS volume fractions.
[0036] FIGS. 11A and 11B depict exemplary graphs showing ethanol (FIG. 11A) and water (FIG. 11B) permeabilities normalized by PDMS volume fraction and morphology factor as a function of PDMS volume fraction.
[0037] FIGS. 12A and 12B depict exemplary graphs showing ethanol (FIG. 12A) and butanol (FIG. 12B) permeabilities for membranes fabricated by EDE397-61 with different amounts of transporting volume fraction, wherein circles show the effect of extra free volume, and triangles show the effect of extra PDMS volume.
[0038] FIG. 13 depicts an exemplary graph showing butanol/water selectivity (circle) and ethanol/water selectivity (triangle) for membranes fabricated by EDE397-61 (from Example 3) with different amounts of free volume. BuOH refers to butanol, and EtOH refers to ethanol.
[0039] FIG. 14 depicts exemplary thermogravimetric analysis (TGA) data for the
hydrogenation product of entry 1 (dashed line) and entry 4 (solid line) of Table 2 in Example 2. [0040] FIG. 15 depicts an exemplary DSC graph showing the second heating/cooling cycle of EDE340-77.
[0041] FIG. 16 depicts an exemplary wide angle x-ray scattering (WAXS) profile of EDE340-77 showing the characteristic Bragg peaks of crystalline polyethylene domains.
[0042] FIG. 17 depicts a process to form a membrane from EDE triblock copolymers.
[0043] FIG. 18 depicts a process to increase the total actual free volume ($rans after) in an EDE triblock copolymer membrane.
[0044] FIG. 19 depicts a flow diagram of a process to produce an EDE triblock copolymer membrane with actual artificial free volume ( AFV)-
[0045] FIG. 20A depicts a plot of small angle X-ray scattering data for a series of EDE129- 41 triblock copolymer membranes constructed using different levels of PDMS homopolymer. The data for the composite membranes were collected after removing the PDMS homopolymer via washing. The filled arrows indicate the primary peak.
[0046] FIG. 20B depicts a plot of small angle X-ray scattering data for a series of EDE209- 45 triblock copolymer membranes constructed using different levels of PDMS homopolymer. The data for the composite membranes were collected after removing the PDMS homopolymer via washing. The filled arrows indicate the primary peak, and the hollow arrows indicate the higher order peaks.
[0047] FIG. 21A depicts a scanning transmission electron microscopy (STEM) image of cyro-microtomed sample of a membrane composed of EDE129-41. The image was collected by a high-angle annular dark field detector.
[0048] FIG. 21B depicts a scanning transmission electron microscopy (STEM) image of cyro-microtomed sample of a membrane composed of EDE129-41/17. The image was collected by a high-angle annular dark field detector.
[0049] FIG. 22A depicts a plot of free- volume cavity size distributions for membranes composed of EDE129-41, EDE129-41/9 and EDE129-41/17. The inset shows a magnification of the large cavity size population. The data was obtained using positron annihilation lifetime spectroscopy (PALS). [0050] FIG. 22B depicts a plot of the relative intensity of the large free- volume cavity size population as a function of the amount of homopolymer blended and washed away for membranes composed of EDE129-41, EDE129-41/9 and EDE129-41/17. The data was obtained using positron annihilation lifetime spectroscopy (PALS).
[0051] FIG. 22C depicts a plot of the relative intensity of the small free-volume cavity size population as a function of the amount of homopolymer blended and washed away
[0052] FIG. 23 depicts a plot of normalized butanol permeability (right y-axis) and normalized ethanol permeability (left y-axis) as a function of theoretical artificial free volume (/ADD, top x-axis) and actual artificial free volume (/AFV, bottom x-axis), for a series of membranes composed of EDE129-41, EDE129-41/9 and EDE129-41/17. The circles with error bars are butanol permeability by the EDE membranes, the squares with error bars are ethanol permeability by the EDE membranes, the black circle without error bars is butanol permeability by a cross-linked PDMS membrane, and the black square without error bars is the ethanol permeability by a cross-linked PDMS membrane.
[0053] FIG. 24 depicts a plot of the ratio of butanol selectivity to water selectivity (left y- axis) and the ratio of butanol selectivity to water selectivity (right y-axis) as a function of theoretical artificial free volume ( ADD, top x-axis) and actual artificial free volume (/AFV, bottom x-axis), for a series of EDE triblock copolymer membranes. The circles with error bars are butanol/water selectivity by the EDE membranes, the squares with error bars are ethanol/water selectivity by the EDE membranes, the black circle without error bars is the butanol/water selectivity by a cross-linked PDMS membrane, and the black square without error bars is the ethanol/water selectivity by a cross-linked PDMS membrane. BuOH refers to butanol, and EtOH referes to ethanol.
[0054] FIG. 25A depicts a plot of ethanol permeability as a function of actual artificial free volume (/AFV) for a series of EDE membranes.
[0055] FIG. 25B depicts a plot of butanol permeability as a function of actual artificial free volume (/AFV) for a series of EDE membranes.
[0056] FIG. 26 depicts a plot of the PALS intensity as a function of cavity diameter for a polyetheylene (PE) homopolymer. [0057] FIG. 27 depicts a plot of actual additional free- volume ( AFV) as a function of theoretical additional free volume (/ADD) for a series of EDE block copolymer membranes.
DETAILED DESCRIPTION
[0058] The following description sets forth numerous exemplary configurations, processes, parameters, and the like. It should be recognized, however, that such description is not intended as a limitation on the scope of the present disclosure, but is instead provided as a description of exemplary embodiments.
[0059] Provided herein are triblock copolymers that may be suitable for selectively separating one or more organic compounds from an aqueous mixture. For example, the triblock copolymers provided herein may be used to selectively separate certain alcohols from a fermentation product mixture.
[0060] The tribock copolymers, methods of producing and using such triblock copolymers are described in further detail below.
Triblock Copolymer
[0061] As used herein, the term "block copolymer" includes polymers that include at least two blocks, where each block contains different polymerized monomer type(s) than the adjacent block or blocks. For example, a "diblock copolymer" may include a polymerized block A and an adjacent polymerized block B, represented as A-B. A "triblock copolymer" may include two polymerized end blocks A flanking a middle polymerized block B, represented as A-B-A.
Alternatively, a triblock copolymer may contain three different polymerized blocks represented as A-B-C.
[0062] In one aspect, provided is a poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer made up of a polydialkylsiloxane block and polyalkylene end blocks. The polyalkylene end blocks may be the same or different. For example, in certain embodiments, such triblock copolymer may have a A-B-A pattern, with a polydialkylsiloxane middle block B and polyalkylene end blocks A flanking the middle block. In other embodiments, such triblock copolymer may have an A-B-C pattern, with a polydialkylsiloxane middle block B and polyalkylene end blocks A and C flanking the middle block. [0063] In some embodiments, the polyalkylene is polyethylene, polypropylene, polyisoprene or polybutadiene. In certain embodiments, the polyalkylene is optionally substituted with halo. In one embodiment, the polyalkylene is optionally substituted with fluoro. In other embodiments, the polydialkylsiloxane is polydimethylsiloxane.
[0064] In another aspect, provided is a triblock colpolymer having a structure of formula (I): x-Y-z (I), wherein:
X and Z are polyalkylene end blocks; and
Y is a polydialkylsiloxane block.
[0065] In some embodiments of the triblock copolymer of formula (I):
X comprises one or more monomeric units independently having a structure of formula
(MO:
Figure imgf000012_0001
Y comprises one or more monomeric units independently having a structure of formula
(My):
Figure imgf000012_0002
Z comprises one or more monomeric units independently having the structure of formula
Figure imgf000013_0001
each R , R , R , R , R and R is independently H, halo, aliphatic or
haloaliphatic.
[0066] The polymeric end blocks may be the same or different. In certain embodiments, X and Z are the same, such that the triblock copolymer may have a structure of formula: X-Y-X or
Z-Y-Z.
[0067] It should be understood that X, Y and/or Z may, in certain embodiments include two or more monomeric units. When X, Y and/or Z include two or more monomeric units, such monomeric units within a given polymeric block may be randomly arranged.
[0068] In certain embodiments of the triblock copolymer of formula (I), each RXA, RXB, RY
R YB , R ZA and R ZB is independently H, halo, alkyl or haloalkyl. In one embodiment, each R XA , RXB, RYA, RYB, RZA and RZB is independently H, F, CH3, CF3, CH2CH3, CH2CH2CH3,
CH2CH2CH2CH3, CH(CH3)2 or C(CH3)3.
[0069] In other embodiments of the triblock copolymer of formula (I), each X and Z is a polymeric block independently comprising one or more monomeric units selected from:
Figure imgf000013_0002
[0070] In certain embodiments, the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer is a poly(ethylene-b-dialkylsiloxane-b-ethylene) triblock copolymer. In certain variations, each X and Z comprises monomeric unit:
Figure imgf000013_0003
[0071] In certain variations, the triblock copolymer has a structure of formula (A):
Figure imgf000014_0001
wherein: each Ra, Rb, Rc and Rd is independently OR1, NRXR2, alkyl, haloalkyl, CN, or H, wherein each R 1 and R 2 is independently H, alkyl or haloalkyl; and each R and R is independently H, halo, aliphatic or haloaliphatic.
[0072] In one variation, the triblock copolymer has a structure of formula (Al):
Figure imgf000014_0002
[0073] It should be understood that in formula (A) and (Al) above, m, n and p refers to the number of repeating units for a given polymeric block. In some embodiments, m and p may be the same.
[0074] For example, each m and p refers to the average number of repeated units in the polyethylene blocks depicted above, wherein: average number of repeating units in polyethylene block =
Mn of polyethylene block
molecular weight of the repeated unit in polyethylene block
A polyethylene block (or hydrogenated polybutadiene) with number average molecular weight 56kDa has an m or p value of 1000, since the repeated unit in hydrogenated polybutadiene has molecular weight of 56.
[0075] In another example, n refers to the average number of repeated units in the polydialkylsiloxane block, wherein: number of repeating units in polydialkylsiloxane block
Mn of polydialkylsiloxane block For example, a polydimethylsiloxane (PDMS) block with number average molecular weight of
74kDa has an n of 1000, since the repeated unit in PDMS has a molecular weight of 74. One of skill in the art would appreciate that the number of units in each block may be determined by any suitable methods known in the art, including for example 1H NMR spectroscopy.
[0076] In certain embodiments, the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer is a poly(propylene-b-dialkylsiloxane-b-propylene) triblock copolymer. In certain embodiments, each X and Z comprises monomeric unit:
Figure imgf000015_0001
[0077] In certain variations, the triblock copolymer has a structure of formula (B):
Figure imgf000015_0002
wherein: each Ra, Rb, Rc and Rd is independently OR1, NRXR2, alkyl, haloalkyl, CN, or H, wherein each R 1 and R 2 is independently H, alkyl or haloalkyl; and each R and R is independently H, halo, aliphatic or haloaliphatic. [0078] In one variation, the triblock copolymer has a structure of formula (Bl):
Figure imgf000015_0003
[0079] It should be understood that in formula (B) and (B 1) above, m, n and p refers to the number of repeating units for a given polymeric block. In some embodiments, m and p may be the same. [0080] In certain embodiments, the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer is a poly(butadiene-b-dialkylsiloxane-b-butadiene) triblock copolymer. In certain variations, each X and Z is a polymeric block comprising monomeric units:
Figure imgf000016_0001
and
[0081] It should be understood that when a polymeric block includes two or more monomeric units, such two or more monomeric units may be randomly arranged in the block. Further, it should be understood that the two or more monomeric units may be present in certain ratios. For exam le in some variations, these monomeric units are present in a ratio of
Figure imgf000016_0002
is between 0.1 to 0.9 and 0.07 to 0.93. [0082] In certain variations, the triblock copolymer has a structure of formula (C):
Figure imgf000016_0004
Figure imgf000016_0003
wherein: each Ra, Rb, Rc and Rd is independently OR1, NRXR2, alkyl, haloalkyl, CN, or H, wherein each R 1 and R 2 is independently H, alkyl or haloalkyl; each R and R is independently H, halo, aliphatic or haloaliphatic; and a and b refer to the number of monomeric units in a polymeric block. [0083] In some variations, the ratio of a : b is between 0.1 : 0.9 and 0.07 : 0.93. [0084] In certain variations, the triblock copolymer has a structure of formula (CI):
Figure imgf000017_0001
[0085] It should be understood that the monomeric units may be randomly arranged in the ends blocks of triblock polymer (C) and (CI). It should further be understood that in formula (C) and (CI) above, m, n and p refers to the number of repeating units for a given polymeric block. In some embodiments, m and p may be the same.
[0086] In certain embodiments, the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer is a poly(isoprene-b-dialkylsiloxane-b-isoprene) triblock copolymer. In certain variations, each X and Z is a polymeric block comprising monomeric units:
Figure imgf000017_0002
[0087] It should be understood that when a polymeric block includes two or more monomeric units, such two or more monomeric units may be randomly arranged in the block. Further, it should be understood that the two or more monomeric units may be present in certain ratios. For example, in some variations, these monomeric units are present in a ratio of
Figure imgf000017_0003
wherein: each Ra, Rb, Rc and Rd is independently OR1, NRXR2, alkyl, haloalkyl, CN, or H, wherein
1 2
each R and R is independently H, alkyl or haloalkyl; each R and R is independently H, halo, aliphatic or haloaliphatic; and a, b and c refer to the number of monomeric units in a polymeric block.
[0089] In some variations, the ratio of a + b : c is between 0.1 : 0.9 and 0.07 : 0.93.
[0090] In certain variations, the triblock copolymer has a structure of formula (Dl):
Figure imgf000018_0001
[0091] It should be understood that the monomeric units may be randomly arranged in the ends blocks of triblock polymer (D) and (Dl). It should further be understood that in formula (D) and (Dl) above, m, n and p refers to the number of repeating units for a given polymeric block. In some embodiments, m and p may be the same.
[0092] In certain embodiments of the triblock copolymer of formula (A), (B), (C) and (D), each Ra, Rb, Rc and Rd is independently OH, NH2, C(CH3)3, CN, or H.
[0093] "Aliphatic" refers to a linear or branched hydrocarbon structure, and can be saturated or have any degree of unsaturation. Aliphatic groups include, for example, alkyl, alkenyl, and alkynyl. In some embodiments, an aliphatic group has I to 10 carbon atoms (i.e. , Ci-io aliphatic group), 1 to 9 carbon atoms (i.e. , C1-9 aliphatic group), 1 to 8 carbon atoms (i.e. , C1-8 aliphatic group), 1 to 7 carbon atoms (i.e. , Cj..7 aliphatic group), 1 to 6 carbon atoms (i.e. , C] .6 aliphatic group ), 1 to 5 carbon atoms (i.e. , C1-5 aliphatic group), 1 to 4 carbon atoms (i.e. , C1-4 aliphatic group), 1 to 3 carbon atoms (i.e. , C1-3 aliphatic), or 1 or 2 carbon atoms (i.e. , C1-2 aliphatic).
[0094] "Alkyl" refers to a linear or branched saturated hydrocarbon chain. In some embodiments, alkyl has 1 to 10 carbon atoms (i.e. , CMO alkyl), 1 to 9 carbon atoms (i.e. , C1 -9 alkyl), 1 to 8 carbon atoms (i.e. , C1-8 alkyl), 1 to 7 carbon atoms (i.e. , C1-7 alkyl), 1 to 6 carbon atoms (i.e. , \.. alkyl), 1 to 5 carbon atoms {i.e., Q.5 alkyl), 1 to 4 carbon atoms (i.e. , C¾..4 alkyl), 1 to 3 carbon atoms (i.e. , C1-3 alkyl), 1 to 2 carbon atoms (i.e. , C1-2 alkyl), or 1 carbon atom (i.e. , Ct alkyl), Examples of alkyl groups include methyl, ethyl, n-propyl, jso-propyl, n-butyl, sec- butyl, ;¾r/-butyl, ra-pentyl, 2-pentyl, wo-pentyl, weo-pentyl, hexyl, 2 -hexyl, 3-hexyl, and 3- methylpentyl. W hen an alkyl residue having a specific number of carbons is named, all geometric isomers having that number of carbons may be encompassed; thus, for example, "butyl" can include w-butyl, sec- butyl, so -butyl and tert-butyl; "propyl" can include ^.-propyl and so-propyl.
[0095] "Alkenyl" refers to a linear or branched hydrocarbon chain with one or more double bonds. In some embodiments, alkenyl has 2 to 10 carbon atoms (i.e., C2-1o alkenyl), 2 to 10 carbon atoms (i.e. , C2-9 alkenyl), 2 to 8 carbon atoms (i.e. , C2-s alkenyl), 2 to 7 carbon atoms (i.e. , C2-7 alkenyl), 2 to 6 carbon atoms (i.e. , C2-6 alkenyl), 2 to 5 carbon atoms (i.e. , C2-5 alkenyl), 2 to 4 carbon atoms (i.e. , C2-4 alkenyl), or 2 or 3 carbon atoms (i.e. , C2-3 alkyl).
[0096] "Alkynyl" refers to a linear or branched hydrocarbon chain with one or more triple bonds. In some embodiments, alkynyl has 2 to 10 carbon atoms (i.e. , C2_io alkynyl), 2 to 10 carbon atoms (i.e. , C2-9 alkynyl), 2 to 8 carbon atoms (i.e. , C2_8 alkynyl), 2 to 7 carbon atoms (i.e. , C2_7 alkynyl), 2 to 6 carbon atoms (i.e. , C2_6 alkynyl), 2 to 5 carbon atoms (i.e. , C2_5 alkynyl), 2 to 4 carbon atoms (i.e. , C2_4 alkynyl), 2 or 3 carbon atoms (i.e. , C2_3 alkynyl).
[0097] "Haloaliphatic" refers a linear or branched hydrocarbon structure, and can be saturated or have any degree of unsaturation, wherein one or more hydrogen atoms are replaced by a halogen. Thus, "haloalkyl" refers to a linear or branched saturated hydrocarbon chain, wherein one or more hydrogen atoms are replaced by a halogen. Similarly, "haloalkenyl" and
"haloalkynyi" refer to a linear or branched hydrocarbon chain with one or more double bonds, or one or more triple bonds, respectively, wherein one or more hydrogen atoms are replaced by a halogen. When two or more hydrogen atoms are replaced by a halogen, the halogen group may be, but are not necessarily, the same halogen; thus, for example, difluoroalkyl, chloro-fluoro- alkyl is within the scope of dihaloalkyl. Other examples of a haloalkyl group include
difluoromethyl (-CHF2) and trifluoromethyl (-CF3).
[0098] As used herein, the terms "polyethylene-polydimethylsiloxane-polyethylene," "ethylene-dimethylsiloxane-ethylene," "poly(ethylene-b-dimethylsiloxane-b-ethylene)," "PE-b- PDMS-b-PE," "PE-PDMS-PE," and "EDE" may be used interchangeably and refer to triblock copolymers including three segments or sections: a polydimethylsiloxane middle block and polyethylene end blocks flanking the middle block. Triblock Copolymers Properties
[0099] The poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein may have one or more of the following properties.
Molecular Weight
[0100] In some embodiments, the triblock copolymers described herein have a molecular weight of at least 110 kg/mol, or between 110 kg/mol and 1000 kg/mol, or between 110 kg/mol and 500 kg/mol. In some embodiments, the triblock copolymers described herein have a molecular weight of at least 50 kg/mol, or between 50 kg/mol and 1000 kg/mol, or between 50 kg/mol and 500 kg/mol, or between 50 kg/mol and 400 kg/mol.
[0101] In certain embodiments, the molecular weight of a triblock copolymer is a number average molecular weight:
Σ, Μ,Ν,
[0102] One of skill in the art would recognize that the number average molecular weight is one way of describing the molecular weight of a polymer. The number average molecular weight is the arithmetic mean or average of the molecular masses of the individual units. The number average molecular weight may be determined by measuring the molecular weight of N polymer molecules, summing the masses, and dividing by N.
[0103] Any suitable methods known in the art may be used to determine molecular weight. For example, the number average molecular weight of a polymer can be determined by gel permeation chromatography, viscometry (e.g., via the Mark-Houwink equation), colligative methods (e.g., vapor pressure osmometry), end-group determination or proton NMR.
Volume Fraction
[0104] In some embodiments, the triblock copolymers described herein have a
polydialkylsiloxane volume fraction between 0.2 and 0.95, between 0.2 and 0.8, or between 0.6 and 0.95.
[0105] Volume fraction of block A ( ΦΑ) is the volume occupied by block A over the total volume of the block copolymer. The volume occupied by block A (VA ) is the product of the volume of each repeated unit for block A times the average number of repeated units of block A
(n) within a reference volume (reference volume = 0.1 nm ):
VA=(nxvolume of repeat unit)/0.1
The volume occupied by block B (VB) is the product of the volume of each repeat unit for block B times the average number of repeat units of block B (m) within a reference volume (reference volume = 0.1 nm ):
VB=(mxvolume of repeat unit)/0.1
For a block copolymer containing two blocks (A+B), the volume fraction of block A is:
Figure imgf000021_0001
[0106] One of skill in the art would recognize how to determine the volume fraction of a triblock copolymer. For example, the volume fractions of the PDMS block of the BDB and EDE copolymers ( PDMS) were determined using monomer volumes of 0.111, 0.138 and 0.119 nm for PBD, PDMS and PE respectively. Thus, in some embodiments, the triblock copolymers described herein have a ^PDMS between 0.2 and 0.95, between 0.2 and 0.8, or between 0.6 and 0.95.
Morphology
[0107] In some embodiments, the triblock copolymers described herein have a morphology capable of providing a continuous transporting phase. It should be understood that "transporting phase" refers to the polydialkylsiloxane-rich microphases. One of skill in the art would recognize that the polydialkylsiloxane and the polyalkylenes are immiscible, and hence the corresponding block copolymers microphase separate and form polydialkylsiloxane-rich microphases polyalkylenes-rich microphases. Microphases may also be referred to as "microdomains."
[0108] In one embodiment, continuous transporting phase refers to the microphase volume fraction with a morphology factor of 1, whereby the morphology factor is a measure of the impedance to transport relative to the transporting phase. In other words, the impedance measurement may be the same as in the transporting phase. In another embodiment, continuous transporting phase refers to the microphase volume fraction that will have the same or greater permeability as the PDMS homopolymer, which is similar to the transporting phase. One of skill in the art would recognize how to measure the continuous transporting phase of a triblock copolymer. For example, continuous transporting phase may be measured by small-angle X-ray scattering, electron microscopy.
[0109] In certain embodiments, the triblock copolymer has a cylindrical, lamellar, double diamond, or gyroid morphology. In one embodiment, the triblock copolymer has a cylindrical or lamellar morphology. In another embodiment, the triblock copolymer has a cylindrical morphology. In yet another embodiment, the triblock copolymer has a lamellar morphology.
[0110] In certain embodiments, "lamellar morphology" includes a phase domain morphology having layers of alternating compositions that generally are oriented parallel with respect to one another. In some embodiments, the domain size is 15-100 nm. In some embodiments, the morphologies are bicontinuous. The term "lamellar morphology" also includes performated lamellae.
[0111] In certain embodiments, "cylindrical morphology" includes a phase domain morphology having discrete tubular or cylindrical shapes. The tubular or cylindrical shapes may be hexagonally packed on a hexagonal lattice. In some embodiments, the domain size is 15-100 nm. In some embodiments, the morphologies are bicontinuous.
[0112] In certain embodiments, "gyroid morphology" includes a phase domain morphology having a network structure with triply connected junctions. In some embodiments, the domain size is 15-100 nm. In some embodiments, the morphologies are bicontinuous.
[0113] In certain embodiments, "double diamond morphology" includes a phase domain morphology having a double-diamond symmetry of space group Pn3m. In some embodiments, the domain size is 15-100 nm. In some embodiments, the morphologies are bicontinuous.
Domain spacing
[0114] In some embodiments, the triblock copolymers described herein have a domain spacing (d) between 10 nm and 90 nm, or between 20 nm and 90 nm. Domain spacing refers to the size of the repeating feature in the microphase separated-material. One of skill in the art would recognize how to measure the domain spacing. For example, domain spacing may be measured by X-ray scattering, electron microscopy. Other Properties
[0115] In other embodiments, the triblock copolymer loses about 5% of weight at a temperature between 400°C and 560°C.
[0116] It should be understood that the triblock copolyers described herein may have one or a combination of the properties described above. For example, in one embodiment, the poly(ethylene-b-dialkylsiloxane-b-ethylene) triblock copolymer has:
(i) a molecular weight between 110 kg/mol and 400 kg/mol; and
(ii) a cylindrical morphology.
[0117] In another embodiment, the poly(ethylene-b-dialkylsiloxane-b-ethylene) triblock copolymer has:
(i) a molecular weight between 110 kg/mol and 400 kg/mol; and
(ii) a lamellar morphology. Triblock Copolymer Compositions
[0118] Provided herein is also a composition made up of any of the triblock copolymers described herein. In some embodiments of such composition, the composition has less than 35 wt , less than 30 wt , less than 25 wt , less than 20 wt , less than 15 wt% or less than 10 wt of polydialkylsiloxane degradants.
[0119] Such degradants may include, for example, poly(dimethylsiloxane) with terminal groups selected from hydroxyl, amino, tert-butyl, nitrile, and H.
[0120] In certain embodiments, the degradants have a structure of formula (X):
Figure imgf000023_0001
wherein:
R and R are as defined in formula (I) above; and Re is OR1, NRXR2, alkyl, haloalkyl, CN, or H, wherein each R1 and R2 is independently
H, alkyl or haloalkyl
Methods of Making Triblock Copolymers
[0121] Provided herein are also methods of producing the poly(alkylene-b-dialkylsiloxane-b- alkylene) triblock copolymers described herein. The approaches for synthesizing polyalkylene, such as polyethylene (PE), and polydialkylsiloxane, such as polydimethylsiloxane (PDMS) known in the art are typically incompatible. For example, PE may be synthesized by metal catalysis, while PDMS may be synthesized by condensation or ring opening polymerization. The methods provided herein address this challenge by providing methods to produce poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymers.
[0122] With reference to FIG. 1, process 1100 is an exemplary reaction to produce poly(ethylene-b-dialkylsiloxane-b-ethylene) (EDE) triblock copolymer 120, wherein RYA and RYB are independently H, halo, aliphatic or haloaliphatic, and Ra, Rb, Rc and Rd are
independently OR 1 , NR1 R2 , alkyl, haloalkyl, CN, or H, and each R 1 and R2 is independently H, alkyl or haloalkyl.
[0123] It should be understood that process 1100 may generally be applied to other types of poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein, including any poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers that may optionally be substituted with one or more halogen atoms, and one of skill in the art would recognize how to make the appropriate modifications.
[0124] Process 1100 involves hydrogenation of poly(l,4-butadiene)-b-polydimethylsiloxane- b-poly(l,4-butadiene) (BDB) 120 in the presence of diazene 110. It should be understood that RYA, RYB, Ra, Rb, Rc and Rd for BDB 120 correspond to the substituents described for compound 130.
[0125] In certain embodiments, the BDB copolymer has a concentration of less than 5 wt , less than 2wt% or less than 1 wt . In certain embodiments, the BDB copolymer is hydrogenated in the presence diazene and solvent. In certain embodiments, the BDB copolymer is soluble in the solvent at a temperature of at least 50°C, or between 65°C and 75°C. The solvent may include an aromatic solvent. In one embodiment, the solvent includes xylene, toluene, naphthalene, or any combinations thereof. [0126] The hydrogenation may be performed at any suitable temperature to yield formation of the triblock copolymer. In certain embodiments, the hydrogenation may be performed at a temperature between 100°C and 125°C.
Diazene
[0127] The diazene used in the methods described herein may be obtained from any commercially available sources, or prepared according to any methods known in the art or any other suitable methods. For example, diazene may be produced by oxidation of hydrazine with hydrogen peroxide or air. Alternatively the decarboxylation of azodicarboxylic acid may also afford diazene.
[0128] Diazene may also be generated by elimination of sulfonohydrazides using a suitable base. For example, 2,4,6-triisopropylbenzenesulfonohydrazide may eliminate diazene upon treatment with sodium bicarbonate, a very mild base.
[0129] In another example, with reference again to FIG. 1, process 1000 depicts an exemplary reaction to produce diazene 110 by thermolysis of sulfonyl hydrazide 102 in the presence of tripropylamine (TPA) 104. With reference to sulfonyl hydrazide 102, Rw may be, for example, H or alkyl; and w may be 0, 1, 2, 3, 4 or 5. Suitable examples of sulfonyl hydrazides include p-toluenesulfonyl hydrazide (TSH). It should be understood that TPA is a proton scavenger in process 1000, and other suitable proton scavengers may be used. The ratio of TSH 102 to TPA 104 used may also vary. In certain embodiments, the sulfonyl hydrazide may have a concentration of less than 20 wt .
Degradants
[0130] The methods described herein may reduce or minimize the side reactions that may occur. For example, with reference again to FIG. 1, one possible side reaction that may occur is diazene disproportionation, as depicted in exemplary process 1200. Another possible side reaction that may occur is PDMS degradation, as depicted in exemplary process 1300. In certain embodiments, the methods provided herein produces less than 35 wt , less than 30 wt , less than 25 wt , less than 20 wt , less than 15 wt , less than 10 wt , less than 5 wt , or less than 1 wt% of polydialkylsiloxane degradants. Such degradants may include, for example, poly(dimethylsiloxane) dihydroxyl terminated, poly(dimethylsiloxane) diamino terminated, poly(dimethylsiloxane) di (tert-butyl ) terminated, poly(dimethylsiloxane) dinitrile terminated, poly(dimethylsiloxane) dihydride terminated, and the degradants have a structure of formula (X) as described above.
BDB copolymer
[0131] BDB copolymer 120 used in process 1100 of FIG. 1 may be obtained from any commercially available sources, or prepared according to any methods known in the art or any other suitable methods.
[0132] For example, FIG. 2 describes an exemplary reaction to produce the BDB copolymer. First, anionic polymerization of 1,3-butadiene 204 may be initiated by sec-BuLi 202 in a solvent, such as cyclohexane, at 50 °C to yield 1,4-polybutadiene (PBD) 220.
[0133] The anionic ring opening polymerization (ROP) of D3 may be carried out using a two- step method. First, hexamethyl(cyclotrisiloxane) monomer (D3 monomer) 230 may be reacted with living PBD anions of polymer 220. This is the initiation step and approximately one D3 monomer is added to each living chain. Then, a promoter, such as tetrahydrofuran 232, may be added to the reaction mixture to give a cyclohexane/tetrahydrofuran mixture. This results in propagation. Temperature may be controlled to reduce side reactions, including for example, backbiting and reshuffling reactions. This allows for control over the propagation reaction at high conversion of the monomer.
[0134] With reference again to FIG. 2, BDB triblock copolymer 250 may be produced by coupling the living poly(l,4-butadiene)-b-polydimethylsiloxanyl lithium polymer chains 240 with l,2-bis-(dimethylhalosilyl)ethane 242 and chlorotrimethylsilane 244.
[0135] Provided herein are also poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymers produced according to any of the methods described herein.
[0136] Provided herein are also methods for producing poly(alkylene-b-dialkylsiloxane-b- alkylene) triblock copolymers by: combining poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer and a polydialkylsiloxane homopolymer to produce a copolymer blend; and washing the copolymer blend to remove at least a portion of the polydialkylsiloxane homopolymer in the copolymer blend. [0137] In one embodiment of the methods of producing the poly(Ct alkylene-b- dialkylsiloxane-b-Ct alkylene) triblock copolymer descirbed herein, the poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer is a
poly(ethylene-b-dialkylsiloxane-b-ethylene) triblock copolymer; and the poly(C2t alkadiene-b-dialkylsiloxane-b-C2t alkadiene) is a poly(butadiene-b- dialkylsiloxane-b-butadiene) triblock copolymer.
[0138] In another embodiment of the methods of producing the poly(Ct alkylene-b- dialkylsiloxane-b-Ct alkylene) triblock copolymer descirbed herein, the poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer is a
poly(propylene-b-dialkylsiloxane-b-propylene) triblock copolymer; and the poly(C2t alkadiene-b-dialkylsiloxane-b-C2t alkadiene) is a poly(hexadiene-b- dialkylsiloxane-b-hexadiene) triblock copolymer.
Triblock Copolymer Membranes
[0139] Provided herein are also membranes made up of poly(alkylene-b-dialkylsiloxane-b- alkylene) triblock copolymers. A membrane is a selective barrier that allows the passage of certain components and retains other components found in a feed solution. It should be understood that the influent of a membrane is generally referred to as the feed-stream; the liquid that passes through the membrane is generally referred to as the permeate; and the liquid containing the retained components is generally referred to as the retentate or concentrate.
[0140] With reference to FIG. 17, depicted is an exemplary membrane 320 made from EDE triblock copolymers, which is produced through exemplary process 300. Each individual EDE triblock copolymer 302 contains a first polyethylene (PE) block 304, a polydimethylsiloxane (PDMS) block 306, and a second PE block 308. In step 310, a plurality of EDE triblock copolymers aggregate based on hydrophobicity of the blocks to form an EDE triblock copolymer membrane. The membrane contains a first microphase 312 of relatively hydrophobic PE blocks, a microphase 314 of relatively hydrophilic PDMS blocks, and a second microphase 316 of relatively hydrophobic PE blocks. The PDMS microphase 314 forms the transporting phase of the membrane. The transporting phase contains free volume 318, which is the free volume associated with the volume fraction of PDMS ( >DMS) present in the entire copolymer membrane. It should be understood that while FIG. 17 depicts a membrane with one PDMS-rich microphase and two PE-rich microphases, membranes as described herein may contain a plurality of PDMS- rich microphase and plurality larger than two of PE-rich microphases.
[0141] Synthetic membranes may be described based on their morphology. Three exemplary types of synthetic membranes include: dense membranes (such as the poly(alkylene- b-dialkylsiloxane-b-alkylene) triblock copolymers), porous membranes (which may be used as support membranes), and asymmetric membranes (which is a combination thereof, and also referred to herein as supported membranes).
[0142] Dense and porous membranes are generally distinct from each other based on the size of separated molecules. Dense membrane is usually a thin layer of dense material utilized in the separation processes of small molecules (usually in gas or liquid phase). Dense membranes may be for gas separations and reverse osmosis applications. Examples of dense membranes includes the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein.
[0143] Porous membranes are typically used in, for example, microfiltration, ultrafiltration, and dialysis applications. The pores of a porous membrane may be a random network of the unevenly shaped structures of different sizes. The formation of a pore can be induced by the dissolution of a "better" solvent into a "poorer" solvent in a polymer solution. Other types of pore structure can be produced by stretching of crystalline structure polymers. The structure of porous membrane is related to the characteristics of the interacting polymer and solvent, components concentration, molecular weight, temperature, and storing time in solution. The thicker porous membranes may, in certain embodiments, provide support for the thin dense membrane layers, forming the asymmetric membrane structures. The latter are usually produced by a lamination of dense and porous membranes.
[0144] In some embodiments, the membrane may be a free-standing membrane made up of any of the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein. A free-standing membrane is unsupported, in contrast to the support membranes described below.
[0145] In other embodiments, the membrane may be a supported membrane. A supported membrane refers to a membrane made up of any of the poly(alkylene-b-dialkylsiloxane-b- alkylene) triblock copolymers described herein, and a porous support. The porous support may be the porous membranes described above. In certain embodiments, the porous membrane is a reverse osmosis membrane, a nanofiltration membrane, or ultrafiltration membrane. In one embodiment, the porous membrane includes polysulfone, polyacrylonitrile, polyvinylidene fluoride, or any combinations thereof.
[0146] The membranes described herein may have one or more of the following properties.
[0147] In some embodiments, the membrane has an average thickness of at least 1 μιη; or between 10 μιη and 200 μιη, between 1 μιη and 100 μιη, between 1 μιη and 50 μιη, or between 10 μιη and 20 μιη. One of skill in the art would recognize that the thickness of a membrane may be measured according to any suitable methods known in the art.
[0148] The supported membranes include a selective layer (referring to the dense membrane layer) and a porous layer (which is a non- selective layer, and is referred to as the support layer). In some embodiments, the supported membrane has an average total thickness of less than 15 μιη. In other embodiments where the average thickness of the selective layer is less than 5 μιη, the average thickness of the porous layer in the supported membrane is less than 10 μιη.
[0149] In some embodiments, the membrane has an ethanol permeability, normalized with the volume fraction of the transporting phase, between 7 mol m/m 2 s Pa and 14 mol m/m 2 s Pa. Triblock Copolymer Blends
[0150] Provided herein are also membranes made up of a blend of polymers, such as any of the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein and a polydialkylsiloxane homopolymer. Such membranes may be produced according to any suitable methods in the art.
[0151] With reference to FIG. 18, depicted is an exemplary membrane made of up a blend of polymers, produced by step 420 of exemplary process 400. A single EDE triblock copolymer 402 contains a first polyethylene (PE) block 404, a polydimethylsiloxane (PDMS) block 406, and a second PE block 408. A plurality of EDE triblock copolymers are combined with a plurality of PDMS homopolymers 410 in step 420. The PE blocks are immiscible with the PDMS blocks and PDMS homopolymers, and the polymer mixture aggregates to form a membrane containing a first microphase 422 and a second microphase 426 comprising PE blocks, and a microphase 314 comprising PDMS. The microphase 314 is the transporting phase of the membrane, and is composed of PDMS blocks 406 and PDMS homopolymers 430. It should be understood that while FIG. 18 depicts a membrane with one PDMS-rich microphase and two PE-rich microphases, membranes as described herein may contain a plurality of PDMS- rich microphase and plurality of PE-rich microphases.
[0152] The membrane may have one or more of the following properties.
[0153] In some embodiments, the membranes made up of a blend of polymers have an average thickness between 5 μιη and 40 μιη.
[0154] In some embodiments, the membranes made up of a blend of polymers have a volume fraction of the polydialkylsiloxane homopolymer in the transporting phase of between 0.01 and 0.2.
[0155] In some embodiments, the membranes made up of a blend of polymers may further include a porous support. In certain embodiments, the porous support may be a porous membrane. In certain embodiments, the porous membrane is a reverse osmosis membrane, a nanofiltration membrane, or an ultrafiltration membrane. In one embodiment, the porous membrane includes polysulfone, polyacrylonitrile, polyvinylidene fluoride, or any combinations thereof.
Poly(alkylene-Z>-dialkylsiloxane-Z>-alkylene) Triblock Copolymer Membranes with
Artificial Free Volume
[0156] Provided herein are also membranes made up of poly(alkylene-b-dialkylsiloxane-b- alkylene) triblock copolymers, wherein the membranes have artificial free volume. In certain embodiments, the membranes with artificial free volume are made up of a blend of polymers, such as any of the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer described herein and a polydialkylsiloxane homopolymer.
[0157] In some embodiments, the artificial free volume is theoretical artificial free volume (/ADD), while in other embodiments, the artificial free volume is actual artificial free volume (/AFV)- Theoretical artificial free volume (/ADD) is the volume fraction of the one or more PDMS microphases occupied by PDMS homopolymer in the blend of polymers, assuming all of the homopolymer resides within the one or more microphasess. Actual artificial free volume (/AFV) is the void in the one or more PDMS microphases left by PDMS homopolymer which has been removed.
[0158] A triblock copolymer membrane with actual artificial free volume may be produced by: combining any of the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein with a polydialkylsiloxane homopolymer to produce a copolymer blend; forming a copolymer blend membrane; and washing the copolymer blend membrane to remove at least a portion of the polydialkylsiloxane homopolymer in the copolymer blend membrane.
[0159] With reference again to FIG. 18, depicted is an exemplary membrane with artificial free volume produced by step 440 of process 400. A single EDE triblock copolymer 402 contains a first polyethylene (PE) block 404, a polydimethylsiloxane (PDMS) block 406, and a second PE block 408. A plurality of EDE triblock copolymers are combined with a plurality of PDMS homopolymers 410 in step 420. The PE blocks are immiscible with the PDMS blocks and PDMS homopolymers, and the polymer mixture aggregates to form a membrane containing a first microphase 422 and a second microphase 426 comprising PE blocks, and a microphase 314 comprising PDMS. The microphase 314 is the transporting phase of the membrane, and is composed of PDMS blocks 406 and PDMS homopolymers 430.
[0160] The free volume 428 in the transporting phase is the free volume associated with the volume fraction of the PDMS block ( PDMS) present in the entire copolymer membrane. The volume fraction of the PDMS microphase occupied by PDMS homopolymer 430 is /ADD- This is the theoretical artificial free volume that may be introduced by removal of the PDMS
homopolymer. The total theoretical free volume of the membrane containing homopolymer is toMs +/ADD = (^rans before, which is also expressed as ^PDMS-
[0161] In step 440, the PDMS homopolymer 430 is removed by dissolution in solvent, producing a membrane comprised of EDE triblock copolymer with transporting phase 444. The total actual free volume 442 of the membrane is PDMS +/AFV = ^rans after, where /AFV is the actual artificial free volume introduced by removal of the PDMS homopolymer.
[0162] FIG. 19 depicts exemplary process 500 to produce an EDE triblock copolymer membrane with artificial free volume. In step 502, EDE triblock copolymers are prepared containing polyethylene (PE) blocks separated by one polydimethylsiloxane (PDMS) block. In step 504, PDMS homopolymers are prepared. The EDE triblock copolymers and the PDMS homopolymers are combined in 506 with a solvent that can at least partially solubilize both polymers. The solution of two polymers is cast on a support in 508. The PE blocks are immiscible with the PDMS blocks and PDMS homopolymers, and in step 510 the polymers aggregate to form a membrane with PE-rich microphases and PDMS-rich microphases. At least a portion of the PDMS-rich microphases form a transporting phase. The membrane is dried and annealed at an elevated temperature in step 512. In step 514, the annealed membrane is washed with a solvent that solubilizes PDMS well, but solubilizes PE poorly. This washing step removes the PDMS homopolymer from the PDSM-rich microphases without removing EDE triblock polymer. Thus, following the washing step, the PDMS-rich microphases phases do not contain PDMS homopolymer, but still contains the PDMS block of the EDE triblock
copolymers. The void left by the removed PDMS homopolymer is the actual artificial free volume ( AFV) introduced into the produced EDE triblock copolymer membrane 518.
[0163] In some embodiments, the membrane with artificial free volume is a free-standing membrane made up of any of the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein. A free-standing membrane is unsupported, in contrast to the support membranes described below.
[0164] In other embodiments, the membrane with artificial free volume is a supported membrane. A supported membrane refers to a membrane made up of any of the poly(alkylene- b-dialkylsiloxane-b-alkylene) triblock copolymers described herein, and a porous support. The porous support may be the porous membranes described above. In certain embodiments, the porous membrane is a reverse osmosis membrane, a nanofiltration membrane, or ultrafiltration membrane. In one embodiment, the porous membrane includes polysulfone, polyacrylonitrile, polyvinylidene fluoride, or any combinations thereof.
[0165] It should be understood that the membranes made up of poly(alkylene-b- dialkylsiloxane-b-alkylene) triblock copolymers with artificial free volume may have any of the one or more properties as described above for the membranes made up of poly(alkylene-b- dialkylsiloxane-b-alkylene) triblock copolymers.
[0166] For example, in some embodiments, the membrane with artificial free volume has an average thickness of at least 1 μιη; or between 10 μιη and 200 μιη, between 1 μιη and 100 μιη, between 1 μιη and 50 μιη, or between 10 μιη and 20 μιη.
[0167] In some embodiments, the supported membranes with artificial free volume include a selective layer (referring to the dense membrane layer) and a porous layer (which is a nonselective layer, and is referred to as the support layer). In some embodiments, the supported membrane has an average total thickness of less than 15 μιη. In other embodiments where the average thickness of the selective layer is less than 5 μιη, the average thickness of the porous layer in the supported membrane is less than 10 μιη.
[0168] In some embodiments, the membrane with artificial free volume has a
polydialkylsiloxane block volume fraction ( PDMS) of between 0.2 and 0.95, between 0.4 and 0.9, between 0.6 and 0.9, or between 0.7 and 0.8.
[0169] In certain embodiments, the membrane with actual artificial free volume has an actual artificial free volume (/AFV) of between 0.02 and 0.5, between 0.05 and 0.45, between 0.05 and 0.3, between 0.02 and 0.35, between 0.1 and 0.35, or between 0.15 and 0.2. In some variations, the membrane with actual artificial free volume has a polydialkylsiloxane block volume fraction ( toMs) of between 0.2 and 0.95, between 0.4 and 0.9, between 0.6 and 0.9, or between 0.7 and 0.8; and an actual artificial free volume ( AFV) of between 0.05 and 0.4, between 0.05 and 0.3, between 0.1 and 0.35, or between 0.15 and 0.2.
[0170] In certain embodiments, the membrane with theoretical artificial free volume has a theoretical artificial free volume (/ADD) of between 0.02 and 0.91, between 0.05 and 0.8, between 0.05 and 0.7, between 0.05 and 0.6, between 0.15 and 0.6, between 0.3 and 0.5, between 0.02 and 0.35, between 0.1 and 0.35, or between 0.15 and 0.2. In some variations, the membrane with theoretical artificial free volume has a polydialkylsiloxane block volume fraction (^DMS) of between 0.2 and 0.95, between 0.4 and 0.9, between 0.6 and 0.9, or between 0.7 and 0.8; and a theoretical artificial free volume (/ADD) of between 0.05 and 0.91, between 0.05 and 0.8, between 0.05 and 0.7, between 0.05 and 0.6, between 0.15 and 0.6, between 0.3 and 0.5, between 0.05 and 0.3, between 0.1 and 0.35, or between 0.15 and 0.2.
[0171] The actual or theoretical artificial free volume can be determined by comparing the total free volume of a membrane with the total free volume of a non-artificial free volume membrane, using relative transport and positron annihilation spectroscopy (PALS), or Xenon NMR or X-ray scattering (depending on the size of the voids).
[0172] In certain variations, the membrane has a non-equilibrium free volume. The non- equilibrium free volume of a membrane is the difference between the total free volume measured before annealing the membrane and the total free volume measured after annealing the membrane. In certain variations, the membrane has a none-equilibrium free volume of between 0.05 and 0.5, between 0.05 and 0.4, between 0.05 and 0.3, between 0.1 and 0.35, or between 0.15 and 0.2.
[0173] In some embodiments, the membrane has a free volume between 0.01 and 0.2. "Free volume" may also be referred to as "void volume" or "pore size". It should be understood that domain spacing may be affected by the presence of voids when the polydialkylsiloxane homopolymer, such as the PDMS homopolymer, is removed. Both the pore-free and pore- containing membranes may have similar volume fractions, but the domain spacing and transport properties may be different for a given thickness of membrane.
[0174] "Free volume" refers to different types of volume in the one or more polymer membranes described herein, including, for example, membranes containing EDE triblock copolymers; membranes containing triblock copolymer blends; and membranes with artificial free volume.
[0175] For example, referring again to FIG. 17, the free volume of membrane 320 made from EDE triblock copolymers is the free volume associated with the volume fraction of PDMS ( toMs) present in the entire copolymer membrane.
[0176] Membranes containing triblock copolymer blends also have different types of free volume. Referring to FIG. 18, the exemplary membrane produced by step 420 is composed of a blend of EDE triblock copolymers and PDMS homopolymers. The types of free volume of this membrane include the free volume associated with the volume fraction of the PDMS block ( toMs) present in the entire copolymer membrane; the volume fraction of PDMS homopolymer present in the membrane, also referred to as "theoretical artificial free volume" (/ADD); and the combination of the free volume associated with the volume fraction of the PDMS blocks ( ^DMS) present in the entire copolymer membrane, and the theoretical artificial free volume (/ADD)- This combination may also be referred to as "total theoretical free volume" ( PDMS + /ADD = ^rans before, which is also expressed as ^PDMS)-
[0177] Membranes composed of triblock copolymers from which homopolymers have been removed also have different types of free volume. With reference again to FIG. 18, the exemplary membrane produced by step 440 is composed of a blend of EDE triblock copolymers from which PDMS homopolymers were removed. The types of free volume of this membrane include the free volume associated with the volume fraction of the PDMS block ( ^DMS) present in the entire copolymer membrane; the volume introduced into the membrane by the removal of the PDMS homopolymers, also referred to as "actual artificial free volume" ( AFV); and the combination of the free volume associated with the volume fraction of the PDMS blocks (^DMS) present in the entire copolymer membrane, and the actual artificial free volume. This combination and may also be referred to as the "total actual free volume" (^DMS + /AFV = ^rans after, which is also expressed as $rans)- In certain embodiments, the actual artificial free volume is the free volume of the membrane in addition to the free volume associated with the volume fraction of the PDMS block (^DMS) present in the entire copolymer membrane.
[0178] In some embodiments, the membrane has a free volume of between 0.2 and 0.95, wherein the free volume refers to the free volume associated with the volume fraction of the PDMS blocks ( PDMS). In some embodiments, the membrane has a free volume of between 0.2 and 0.92, wherein free volume is the theoretical artificial free volume. In other embodiments, membrane has a free volume of between 0.2 and 0.95, wherein free volume is the total theoretical free volume. In yet other embodiments, the membrane has a free volume of between 0.1 and 0.4, wherein free volume is the actual artificial free volume. In still other embodiments, the membrane has a free volume of between 0.2 and 0.95, wherein the free volume is the total actual free volume.
[0179] In certain embodiments, "free volume" (more specifically the actual artificial free volume) may be the volume fraction of polydialkylsiloxane homopolymer, such as PDMS homopolymer, that was in the block copolymer, and may be defined as the percentage ( ) of total volume.
[0180] In certain embodiments, the total free volume of a membrane is the summation of all the types of free volume (e.g. , "void volume" or "pore size") present in that membrane. For example, in certain embodiments, the total free volume of a membrane is the free volume associated with the volume fraction of the PDMS blocks ( PDMS) present in the entire copolymer membrane. In other embodiments, the total free volume is the total actual free volume. In certain embodiments, the total free volume of a membrane described herein is between 0.2 and 0.95, between 0.2 and 0.8, between 0.3 and 0.7, between 0.35 and 0.65, or between 0.35 and 0.45.
[0181] Free volume may be measured by looking at relative transport and positron annihilation spectroscopy (PALS), or Xenon NMR or X-ray scattering (depending on the size of the voids). Methods of Using the Triblock Copolymers
[0182] Provided herein are also methods of separating one or more organic compounds from an aqueous mixture of organic compounds. The methods involve contacting the aqueous mixture with any of the membranes described herein, including any membranes made up the poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers described herein, to separate one or more organic compounds from the aqueous mixture, and one or more of the organic compounds in the aqueous mixture selectively permeates through the membrane.
[0183] In general, the copolymer compositions described herein may be hydrophobic to hinder the permeation of water molecules. Additionally, the copolymer compositions described herein contain a structural block that imparts essential mechanical properties to the membrane (e.g., polyalkylene) and an alcohol transporting block (e.g., polydialkylsiloxane).
[0184] In some embodiments, the methods disclosed herein separate the one or more organic compounds from an aqueous solution produced in a fermentation process. The separation is carried out using pervaporation techniques known in the art and described herein.
[0185] In other embodiments, the one or more organic compounds include acetic acid, formic acid, levulinic acid, succinic acid, furfural, 5-hydroxymethylfurfural, 2-furoic acid, vanillic acid, ferulic acid, p-coumaric acid, syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid), 4-hydroxybenzoic acid; protocatechuic acid (3,4-dihydroxybenzoic acid); homovanillic acid (2-(4-hydroxy-3-methoxy-phenyl)acetic acid); caffeic acid (3,4-dihydroxycinnamic acid); sinapic acid; propionic acid; vanillylmandelic acid; 4-hydroxymandelic acid; 4- hydroxyphenylacetic acid; 3-hydroxybenzoic acid; 2,5-dihydroxybenzoic acid; benzoic acid; vanillin; syringaldehyde; 4-hydroxybenzaldehyde; coniferyl aldehyde (4-OH-3-OCH3- cinnamaldehyde); sinapinaldehyde (3,5-dimethoxy-4-hydroxycinnamaldehyde);
protocatechualdehyde (3,4-dihydroxybenzaldehyde); acetovanillone (4'-hydroxy-3'- methoxyacetophenone); acetosyringone (3',5'-dimethoxy-4'-hydroxyacetophenone); guaiacol; coniferyl alcohol (4-(3-hydroxy-l-propenyl)-2-methoxyphenol); hydroquinone; catechol (pyrocatechol); vanillyl alcohol (4-hydroxy-3-methoxybenzyl alcohol); eugenol; or any mixture or combination thereof. In certain embodiments, the one or more organic compounds include acetic acid, formic acid, levulinic acid, succinic acid, furfural, 5-hydroxymethylfurfural, or any mixture or combination thereof. In one embodiment, the one or more organic compounds is 5- hydroxymethylfurfural. In another embodiment, the one or more organic compounds include furfural. [0186] In some embodiments, the one or more organic compounds include one or more alcohols, such as, for example, ethanol, butanol, or any combination thereof. In certain embodiments, the one or more organic compounds include one or more C2-10 alcohols. In some embodiments, the one or more organic compounds separated include ethanol, w-butanol, isobutanol, 2-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, or 1-decanol, or any combination thereof.
[0187] In other embodiments, the one or more organic compounds include acetone. In other embodiments, the one or more organic compounds include acetone, ethanol, and w-butanol produced in an acetone-ethanol-w-butanol (ABE) fermentation process. In other embodiments, the one or more organic compounds include one or more byproducts produced in a fermentation process. In some embodiments, the one or more organic compounds that are suitable for such separation processes are hydrophobic so they are able to permeate through the membrane and have a boiling point in the range that is suitable for pervaporation.
[0188] The one or more organic compound may be obtained from a renewable or biological source.
[0189] The membrane used to separate such one or more compounds may, in certain embodiments, have a separation factor (MSF) between 1.0 to 4.0. In some embodiments, the method to separate the one or more organic compounds may be performed at a temperature of at least 100°C.
[0190] In certain embodiments, the membrane used to separate the one or more organic compounds has a ratio of the permeability of the one or more organic compounds to the permeability of water of between 1.0 and 4.0, between 2.0 and 4.0, or between 3.0 and 4.0. In some variations, the membrane used to separate the one or more organic compounds has a ratio of the permeability of butanol to the permeability of water of between 1.0 and 4.0, between 2.0 and 4.0, or between 3.0 and 4.0. In some embodiments, the method to separate the one or more organic compounds may be performed at a temperature of at least 100°C.
[0191] Provided herein are also one or more organic compounds produced according to any one of the methods described herein. Such one or more organic compounds may be selected from the group consisting of acetone, ethanol, w-butanol, isobutanol, 2-butanol, 1-pentanol, 1- hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, acetic acid, formic acid, levulinic acid, succinic acid, furfural, 5-hydroxymethylfurfural, 2-furoic acid, vanillic acid, ferulic acid, p- coumaric acid, syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid), 4-hydroxybenzoic acid, protocatechuic acid (3,4-dihydroxybenzoic acid), homovanillic acid (2-(4-hydroxy-3-methoxy- phenyl)acetic acid), caffeic acid (3,4-dihydroxycinnamic acid), sinapic acid, propionic acid, vaniUylmandelic acid, 4-hydroxymandelic acid, 4-hydroxyphenylacetic acid, 3-hydroxybenzoic acid, 2,5-dihydroxybenzoic acid, benzoic acid, vanillin, syringaldehyde, 4- hydroxybenzaldehyde, coniferyl aldehyde (4-OH-3-OCH3-cinnamaldehyde), sinapinaldehyde (3,5-dimethoxy-4-hydroxycinnamaldehyde), protocatechualdehyde (3,4- dihydroxybenzaldehyde), acetovanillone (4'-hydroxy-3'-methoxyacetophenone), acetosyringone (3',5'-dimethoxy-4'-hydroxyacetophenone), guaiacol, coniferyl alcohol (4- (3 -hydroxy- 1- propenyl)-2-methoxyphenol), hydroquinone, catechol (pyrocatechol), vanillyl alcohol (4- hydroxy-3-methoxybenzyl alcohol), eugenol, and any combinations thereof.
ENUMERATED EMBODIMENTS
[0192] The following enumerated embodiments are representative of some aspects of the invention.
1. A poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer comprising a polydialkylsiloxane block and polyalkylene end blocks, wherein the triblock copolymer has a molecular weight of at least 110 kg/mol, and wherein the polyalkylene is optionally substituted with halo.
2. The triblock copolymer of embodiment 1, wherein the triblock copolymer has one or more of the following properties (i) to (iii):
(i) a polydialkylsiloxane volume fraction between 0.2 and 0.95;
(ii) a morphology capable of providing a continuous transporting phase; and
(iii) a domain spacing (d) between 10 nm and 90 nm.
3. The triblock copolymer of embodiment 1 or 2, wherein the poly(ethylene-b- dialkylsiloxane-b-ethylene) triblock copolymer has a molecular weight between 110 kg/mol and 400 kg/mol.
4. The triblock copolymer of any one of embodiments 1 to 3, wherein the morphology is cylindrical, lamellar, double diamond, or gyroid. 5. The triblock copolymer of any one of embodiments 1 to 4, wherein the polyalkylene is polyethylene, polypropylene, polyisoprene or polybutadiene.
6. The triblock copolymer of any one of embodiments 1 to 5, wherein the
polydialkylsiloxane is polydimethylsiloxane.
7. The triblock copolymer of any one of embodiments 1 to 6, wherein the triblock copolymer has a structure of formula (I): x-Y-z (I), wherein:
X is a polymeric block comprising one or more monomeric units independently having a structure of formula (Mx):
Figure imgf000039_0001
Y is a polymeric block comprising one or more monomeric units independently having a structure of formula (My):
Figure imgf000039_0002
Z is a polymeric block comprising one or more monomeric units independently having the structure of formula (Mz):
Figure imgf000039_0003
each R , R , R , R , R and R is independently H, halo, aliphatic or
haloaliphatic.
8. A method of producing a poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer, wherein t is an integer greater than or equal to 2, the method comprising
hydrogenating a poly(C2t alkadiene-b-dialkylsiloxane-b-C2t alkadiene) triblock copolymer in the presence of diazene to produce the poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer.
9. The method of embodiment 8, wherein the poly(C2t alkadiene-b-dialkylsiloxane-b-C2t alkadiene) triblock copolymer is hydrogenated in the presence diazene and solvent.
10. The method of embodiment 9, wherein the poly(C2t alkadiene-b-dialkylsiloxane-b-C2t alkadiene) triblock copolymer is soluble in the solvent at a temperature of at least 50°C.
11. The method of embodiment 9, wherein the solvent comprises aromatic solvent.
12. The method of embodiment 9, wherein the solvent comprises xylene, toluene, naphthalene, or any combinations thereof.
13. The method of any one of embodiments 8 to 12, wherein the hydrogenation is performed at a temperature between 100°C and 125°C.
14. The method of any one of embodiments 8 to 12, further comprising combining p- toluenesulfonyl hydrazide and a proton scavenger to produce the diazene.
15. The method of embodiment 14, wherein the proton scavenger is tripropylamine.
16. The method of embodiment 14 or 15, wherein the p-toluenesulfonyl hydrazide has a concentration of less than 20 wt .
17. The method of any one of embodiments 8 to 16, wherein the poly(C2t alkadiene-b- dialkylsiloxane-b-C2t alkadiene) triblock copolymer has a concentration of less than 1 wt .
18. The method of any one of embodiments 8 to 17, wherein the method produces less than 35 wt% of polydialkylsiloxane degradants.
19. The method of any one of embodiments 8 to 18, further comprising: combining the poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer and a polydialkylsiloxane homopolymer to produce a copolymer blend; and washing the copolymer blend to remove at least a portion of the polydialkylsiloxane homopolymer in the copolymer blend.
20. The method of any one of embodiments 8 to 19, wherein: the poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer is a poly(ethylene-b-dialkylsiloxane-b-ethylene) triblock copolymer; and the poly(C2t alkadiene-b-dialkylsiloxane-b-C2t alkadiene) is a poly(butadiene-b- dialkylsiloxane-b-butadiene) triblock copolymer.
21. The method of any one of embodiments 8 to 19, wherein: the poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer is a poly(propylene-b-dialkylsiloxane-b-propylene) triblock copolymer; and the poly(C2t alkadiene-b-dialkylsiloxane-b-C2t alkadiene) is a poly(hexadiene-b- dialkylsiloxane-b-hexadiene) triblock copolymer.
22. A poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer produced according to the method of any one of embodiments 8 to 21.
23. A membrane comprising a poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer, wherein the membrane has one or more of the following properties (i) to (iv):
(i) an average thickness of at least 1 μιη;
(ii) a free volume between 0.01 and 0.2; and
(iii) an ethanol permeability, normalized with the volume fraction of the transporting phase, between 7 mol m/m 2 s Pa and 14 mol m/m 2 s Pa.
24. The membrane of embodiment 23, wherein the copolymer is a copolymer of any one of embodiments 1 to 7 and 22.
25. The membrane of embodiment 23 or 24, wherein the membrane is free-standing.
26. A membrane comprising: a poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer of any one of claims 1 to 7 and 22; and a polydialkylsiloxane homopolymer.
27. The membrane of embodiment 26, wherein the membrane has one or both of the following properties (i) and (ii): (i) an average thickness between 5 μηι and 40 μηι; and
(ii) a volume fraction of the polydialkylsiloxane homopolymer in the transporting phase of between 0.01 and 0.2.
28. A membrane, comprising:
(i) a polymer membrane comprising a poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer according to any one of embodiments 1 to 7 and 22, or a membrane of any one of embodiments 23 to 27; and
(ii) a porous support.
29. The membrane of embodiment 28, wherein the porous support is a reverse osmosis membrane, a nanofiltration membrane, or an ultrafiltration membrane.
30. The membrane of embodiment 28 or 29, wherein the porous support comprises polysulfone, polyacrylonitrile, polyvinylidene fluoride, or any combinations thereof.
31. The membrane of any one of embodiments 28 to 30, wherein the membrane has a thickness of at least 9 μιη.
32. A method of separating one or more organic compounds from an aqueous mixture of organic compounds, the method comprising contacting the aqueous mixture with a membrane to separate one or more organic compounds from the aqueous mixture, wherein (i) the membrane comprises a poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer according to any one of embodiments 1 to 7 and 22, or (ii) the membrane is a membrane according to any one of embodiments 23 to 31 ; and wherein one or more of the organic compounds in the aqueous mixture selectively permeates through the membrane.
33. The method of embodiment 32, wherein the one or more organic compounds are selected from the group consisting of acetone, ethanol, w-butanol, isobutanol, 2-butanol, 1-pentanol, 1- hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, acetic acid, formic acid, levulinic acid, succinic acid, furfural, 5-hydroxymethylfurfural, 2-furoic acid, vanillic acid, ferulic acid, p- coumaric acid, syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid), 4-hydroxybenzoic acid, protocatechuic acid (3,4-dihydroxybenzoic acid), homovanillic acid (2-(4-hydroxy-3-methoxy- phenyl)acetic acid), caffeic acid (3,4-dihydroxycinnamic acid), sinapic acid, propionic acid, vaniUylmandelic acid, 4-hydroxymandelic acid, 4-hydroxyphenylacetic acid, 3-hydroxybenzoic acid, 2,5-dihydroxybenzoic acid, benzoic acid, vanillin, syringaldehyde, 4- hydroxybenzaldehyde, coniferyl aldehyde (4-OH-3-OCH3-cinnamaldehyde), sinapinaldehyde (3,5-dimethoxy-4-hydroxycinnamaldehyde), protocatechualdehyde (3,4- dihydroxybenzaldehyde), acetovanillone (4'-hydroxy-3'-methoxyacetophenone), acetosyringone (3',5'-dimethoxy-4'-hydroxyacetophenone), guaiacol, coniferyl alcohol (4- (3 -hydroxy- 1- propenyl)-2-methoxyphenol), hydroquinone, catechol (pyrocatechol), vanillyl alcohol (4- hydroxy-3-methoxybenzyl alcohol), eugenol, and any combinations thereof.
34. The method of embodiment 33, wherein the one or more organic compounds are one or more alcohols.
35. The method of embodiment 34, wherein the one or more alcohols are ethanol, butanol, or a combination thereof.
36. The method of any one of embodiments 33 to 35, wherein the one or more organic compounds separated are one or more C2-io alcohols.
37. The method of embodiment 36, wherein the one or more organic compounds separated are selected from the group consisting of ethanol, w-butanol, isobutanol, 2-butanol, 1-pentanol, 1- hexanol, 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol.
38. The method of any one of embodiments 32 to 37, wherein the one or more organic compound are obtained from a renewable or biological source.
39. The method of any one of embodiments 32 to 38, wherein the membrane has a separation factor (MSF) between 1.0 to 4.0.
40. A membrane, comprising a plurality of poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers, wherein each triblock copolymer comprises a first polyalkylene end block and a second polyalkylene end block separated by a polydialkylsiloxane block; and wherein at least a portion of the plurality of triblock copolymers is aggregated to form one or more polyalkylene-rich microphases and one or more polydialkylsiloxane- rich microphases. 41. The membrane of embodiment 40, wherein the membrane has one or more of the following properties (i) to (vii):
(i) a polydialkylsiloxane block volume fraction (^DMS) between 0.2 and 0.95;
(ii) a domain spacing (d) between 10 nm and 90 nm;
(iii) a molecular weight between 50 kg/mol and 400 kg/mol;
(iv) an average thickness of at least 1 μιη;
(v) an ethanol permeability, normalized with the volume fraction of the transporting phase, of between 7 mol m/m 2 s Pa and 14 mol m/m 2 s Pa;
(vi) a ratio of the permeability of one or more organic compounds to the permeability of water of between 1.0 to 4.0; and
(vii) is free standing.
42. The membrane of embodiment 40 or 41, further comprising one or more
polydialkylsiloxane homopolymers.
43. The membrane of embodiment 42, wherein: at least a portion of the one or more polydialkylsiloxane homopolymers and at least a portion of the plurality of triblock copolymers are aggregated to form the one or more polydialkylsiloxane-rich microphases.
44. The membrane of embodiment 43, wherein the triblock copolymer has a theoretical artificial free volume (/ADD), wherein the theoretical artificial free volume is the volume fraction of the one or more polydialkylsiloxane-rich microphases occupied by the at least a portion of the one or more polydialkylsiloxane homopolymers; and wherein the theoretical artificial free volume is between 0.02 and 0.80.
45. The membrane of embodiment 44, wherein the theoretical artificial free volume is between 0.05 and 0.60. 46. The membrane of embodiment 44, wherein the theoretical artificial free volume is between 0.05 and 0.40.
47. The membrane of any one of embodiments 40 or 43 to 46, wherein the triblock copolymer has an actual artificial free volume ( AFVX wherein the actual artificial free volume is the volume produced by removal of one or more polydialkylsiloxane homopolymers from the transporting phase; and wherein the actual artificial free volume is between 0.02 and 0.45.
48. The membrane of embodiment 47, wherein the membrane has polydialkylsiloxane block volume fraction ( PDMS) of between 0.7 and 0.8, and an actual artificial free volume ( AFV) of between 0.15 and 0.20.
49. The membrane of embodiment 40, wherein the membrane has a non-equilibrium free volume, wherein the non-equilibrium free volume is the difference in total free volume measured before annealing and the total free volume measured after annealing.
50. The membrane of embodiment 49, wherein the non-equilibrium free volume is between 0.05 and 0.4.
51. The membrane of embodiment 40, wherein the membrane has an actual artificial free volume, wherein the actual artificial free volume is the free volume of the membrane in addition to the free volume associated with the polydialkylsiloxane block volume fraction
Figure imgf000045_0001
wherein the actual artificial free volume is between 0.02 and 0.45.
52. A membrane, comprising a plurality of poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers and a plurality of polydialkylsiloxane homopolymers, wherein each triblock copolymer comprises a first polyalkylene end block and a second polyalkylene end block separated by a polydialkylsiloxane block; wherein at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of polydialkylsiloxane homopolymers are aggregated to form one or more polyalkylene -rich microphases and one or more polydialkylsiloxane-rich microphases.
53. The membrane of embodiment 52, further comprising a solvent.
54. The membrane of any one of embodiments 40 to 53, wherein the polyalkylene is polyethylene, polypropylene, polyisoprene or polybutadiene.
55. The membrane of any one of embodiments 40 to 53, wherein the polyalkylene end blocks are independently optionally substituted with halo.
56. The membrane of any one of embodiments 40 to 55, wherein the polydialkylsiloxane is polydimethylsiloxane.
57. A supported membrane, comprising
(i) a membrane according to any one of embodiments 40 to 56; and
(ii) a porous support.
58. The supported membrane of embodiment 57, wherein the porous support is a reverse osmosis membrane, a nanofiltration membrane, or an ultrafiltration membrane.
59. The supported membrane of embodiment 57 or 58, wherein the porous support comprises polysulfone, polyacrylonitrile, polyvinylidene fluoride, or any combinations thereof.
60. The supported membrane of any one of embodiments 57 to 59, wherein the membrane has an average thickness of at least 9 μιη.
61. A method of separating one or more organic compounds from an aqueous mixture of organic compounds, the method comprising contacting the aqueous mixture with a membrane to separate one or more organic compounds from the aqueous mixture, wherein the membrane is a membrane according to any one of embodiments 40 to 56, or a supported membrane according to any one of embodiments 57 to 60; and wherein one or more of the organic compounds in the aqueous mixture selectively permeates through the membrane. 62. The method of embodiment 61, wherein the one or more organic compounds are selected from the group consisting of acetone, ethanol, w-butanol, isobutanol, 2-butanol, 1-pentanol, 1- hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, acetic acid, formic acid, levulinic acid, succinic acid, furfural, 5-hydroxymethylfurfural, 2-furoic acid, vanillic acid, ferulic acid, p- coumaric acid, syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid), 4-hydroxybenzoic acid, protocatechuic acid (3,4-dihydroxybenzoic acid), homovanillic acid (2-(4-hydroxy-3-methoxy- phenyl)acetic acid), caffeic acid (3,4-dihydroxycinnamic acid), sinapic acid, propionic acid, vaniUylmandelic acid, 4-hydroxymandelic acid, 4-hydroxyphenylacetic acid, 3-hydroxybenzoic acid, 2,5-dihydroxybenzoic acid, benzoic acid, vanillin, syringaldehyde, 4- hydroxybenzaldehyde, coniferyl aldehyde (4-OH-3-OCH3-cinnamaldehyde), sinapinaldehyde (3,5-dimethoxy-4-hydroxycinnamaldehyde), protocatechualdehyde (3,4- dihydroxybenzaldehyde), acetovanillone (4'-hydroxy-3'-methoxyacetophenone), acetosyringone (3',5'-dimethoxy-4'-hydroxyacetophenone), guaiacol, coniferyl alcohol (4- (3 -hydroxy- 1- propenyl)-2-methoxyphenol), hydroquinone, catechol (pyrocatechol), vanillyl alcohol (4- hydroxy-3-methoxybenzyl alcohol), eugenol, and any combinations thereof.
63. The method of embodiment 62, wherein the one or more organic compounds are one or more alcohols.
64. The method of embodiment 63, wherein the one or more alcohols are ethanol, butanol, or a combination thereof.
65. The method of embodiment 62, wherein the one or more organic compounds separated are selected from the group consisting of ethanol, w-butanol, isobutanol, 2-butanol, 1-pentanol, 1- hexanol, 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol.
66. The method of any one of embodiments 61 to 65, wherein the one or more organic compound are obtained from a renewable or biological source.
67. The method of any one of embodiments 61 to 66, wherein the ratio of the permeability of the one or more organic compounds to the permeability of water is between 1.0 to 4.0.
68. A method of producing a membrane, the method comprising: providing a plurality of poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers; providing a plurality of polydialkylsiloxane homopolymers; combining the plurality of triblock copolymers, the plurality of homopolymers, and a first solvent to form a polymer mixture, wherein the first solvent solubilizes at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of homopolymers; and casting the polymer mixture to produce a membrane, wherein the membrane comprises at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of homopolymers.
69. The method of embodiment 68, further comprising annealing the membrane.
70. The method of embodiment 68 or 69, further comprising: contacting the membrane with a second solvent, wherein the second solvent solubilizes at least a portion of the plurality of homopolymers; and removing at least a portion of the solubilized homopolymers.
71. A poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer comprising a polydialkylsiloxane block and polyalkylene end blocks, wherein the triblock copolymer has a molecular weight of at least 50 kg/mol, and wherein the polyalkylene is optionally substituted with halo.
72. The triblock copolymer of embodiment 71, wherein the triblock copolymer has one or more of the following properties (i) to (v):
(i) a polydialkylsiloxane volume fraction between 0.2 and 0.95;
(ii) a morphology capable of providing a continuous transporting phase;
(iii) a domain spacing (d) between 10 nm and 90 nm;
(iv) a cylindrical, lamellar, double diamond, or gyroid morphology; and
(v) a molecular weight between 50 kg/mol and 400 kg/mol.
73. A method of producing a poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer, wherein t is an integer greater than or equal to 2, the method comprising
hydrogenating a poly(C2t alkadiene-b-dialkylsiloxane-b-C2t alkadiene) triblock copolymer in the presence of diazene to produce the poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer. EXAMPLES
[0193] The following Examples are merely illustrative and are not meant to limit any aspects of the present disclosure in any way.
[0194] All reactions performed in the Examples below were carried out by standard high vacuum techniques and glove box operations, unless otherwise stated.
Materials
[0195] 1,3-Butadiene (Aldrich, 99%) was purified by drying an appropriate amount of monomer over finely ground CaH2 overnight, followed by distillation in activated molecular sieves where it remained in contact overnight. The butadiene was then vacuum-transferred to a reactor containing n-BuLi where it remained with continuous stirring at 0 °C for 1 hour. The resulting monomer was distilled in a reactor containing toluene that had been dried as described below. The monomer was stored at -20 °C in the glove box and was used within the period of 2 weeks.
[0196] Toluene was purified by passing through solvent purification columns followed by stirring overnight over finely ground CaH2. The toluene was then distilled and stored in a reactor over polystyryl lithium obtaining the characteristic red color.
[0197] Sec-Buhi (Aldrich, 1.7 M in cyclohexane) was titrated using 1,3-diphenylacetone p- tosylhydrazone to confirm the concentration of active species. The sec-BuLi was used without any additional treatment.
[0198] THF was purified by passing through solvent purification columns followed by stirring overnight over finely ground CaH2 and then stored in a reactor over a Na/benzophenone mixture obtaining the characteristic blue color.
[0199] Hexamethylcyclotrisiloxane, D3, (Gelest, 95 %) was purified as follows: D3 was melted by heating at 80 °C, put in a flask, diluted by an equal amount of purified cyclohexane, and stirred overnight over CaH2. Then the solvent along with the monomer was distilled into a flask containing polystyryl lithium. The monomer was in contact with polystyryl lithium for about 2 hours at room temperature and then it was distilled into a flame dried reactor along with the solvent by heating at 80 °C. Finally, the monomer was isolated by distilling cyclohexane to another reactor at room temperature. The reactor containing D3 was transferred and stored in the glove box. [0200] l,2-Bis-(dimethylchlorosilyl)ethane (Aldrich) was purified by fractional distillation on the vacuum line and then stored in the glove box.
[0201] All other solvents were distilled on the vacuum line prior to use, unless otherwise stated.
General Characterization Protocols
[0202] Gel Permeation Chromatography (GPC): n and dispersities, D , of the BDB precursors were obtained using a Viscotek TDA 302 GPC system that has a guard column, a set of four Viscotek columns (300 mm x 7.8 mm, T-3000, T-4000, T-5000, and T-6000 columns) and a refractive index detector, with THF eluent (flow rate of 1 mL/min, 35 °C). The instrument was calibrated with polystyrene standards (Agilent Easivials PS-M). The molecular weights of the poly(l,4-butadiene) precursors were calculated based on triple detection experiments.
[0203] High Temperature Gel Permeation Chromatography (GPC): n and dispersities, D, of the polymers was characterized by gel permeation chromatograph (GPC) using a Malvern Viscotek HT-GPC system with 3 Tosoh GMHhr-H(S) HT columns. The samples were analyzed in a mobile phase of 1,2,4-trichlorobenzene with 500 ppm BHT at 145 C. The polymers were dissolved in the mobile phase for 1 hour at 145 °C prior to injection into the
system. Conventional calibration using polystyrene standards (Malvern Instruments Inc.) was used to determine the molecular weight.
[0204] Nuclear Magnetic Resonance (NMR) Spectroscopy: 1H NMR measurement was conducted on 500 MHz Bruker DRX 500 spectrometer using deuterated solvents purchased by Aldrich. The solutions for 1H NMR spectra had a polymer concentration of - 10 mg/mL.
Polymers post hydrogenation were analyzed at 80 °C to achieve solubilization of the
polyethylene segments. Spectra were analyzed to determine copolymer compositions as well as hydrogenation and degradation percentages.
[0205] Thermogravimetric Analysis (TGA): TGA experiments were performed on a "TGA Q20" instrument from TA Instruments under nitrogen flow rate of 100 mL/min. In the first step, the samples were heated from 30 to 110 °C at 10 °C/min, and the temperature was maintained at 110 °C for 1 h. In the second step, the samples were cooled down to 30 °C at 10 °C/min and heated again at 10 °C/min until the temperature reached 600 °C. [0206] Differential Scanning Calorimetry (DSC): DSC experiments were performed on a Thermal Advantage Q200 calorimeter at the joint center of artificial photosynthesis (JCAP), Lawrence Berkeley National Laboratory. Samples were sealed in aluminum hermetic pans. DSC scans consisted of two heating/cooling cycles and were conducted over the range 0-150 °C at a rate of 10 °C/min. The glass transition temperatures ( g) for EDE32-335, presented here is from the inflection point of the transition in the second heating run. The enthalpy of fusion of the first heating cycle was used in order to estimate the degree of crystallinity of polyethylene and the polyethylene phase in the EDE triblock copolymer samples by comparing it to the enthalpy of fusion of 100% crystalline polyethylene. A value of 4.11 kJ per repeating unit was used to estimate the enthalpy of fusion of 100% crystalline polyethylene.
[0207] Small angle x-ray scattering (SAXS) and Wide angle x-ray scattering (WAXS):
0.1 mm thick EDE samples were prepared solvent casting as described in a previous section. Synchrotron small-angle X-ray scattering (SAXS) and wide angle x-ray scattering (WAXS) measurements were performed using the 7.3.3 beamline at the Advanced Light Source (ALS, Lawrence Berkeley National Laboratory). At the ALS, the wavelength λ of the incident X-ray beam was 0.124 nm (Δλ/λ = 10^), and a sample-to-detector distance of 4 m was used for the SAXS measurements. The resulting two-dimensional scattering data were averaged azimuthally to obtain intensity versus magnitude of the scattering wave vector q (q = 4π sin(9/2)/ , where Θ is the scattering angle). The scattering data were corrected for the detector dark current and the scattering from air and Kapton windows.
[0208] Scanning Transmission Electron Microscopy (STEM): Thin sections with thickness of approximately 120 nm were obtained by cryo-microtoming at -120 °C using a Leica EM FC6 and picked up on a lacey carbon coated copper grid (Electron Microscopy Sciences). Scanning transmission electron microscopy experiments were performed on a Tecnai F20 UT FEG, equipped with a high angle annular dark field (HAADF) detector, using 200 keV acceleration voltage.
[0209] Positron Annihilation Lifetime Spectroscopy (PALS): PALS was used to determine the free volume within membranes by measuring the lifetime of positrons within the polymer membranes before they annihilate due to interactions with the material. Positrons form a bound state with free electrons within the membranes with the same spin state (oPs). The oPs is attracted to areas of low electron density (free volume) and annihilate when interacting with electrons from the membrane. Therefore, a relationship between the size of the free volume elements within the sample can be made with the lifetime of the oPs. The Tao-Eldrup equation was used to calculate the average free volume using the oPs lifetime (τ3);
Figure imgf000052_0001
[0210] The semi-empirical equation assumes an infinite spherical potential well model where R is the radius of the free volume elements and Ro = R + AR (where AR was calculated to be
1.66A due to the thickness of the electron layer within the potential well of radius Ro). The fractional free volume (FFV) was calculated assuming spherical free volume elements using the radius determined from the lifetime (R) and the associated Intensity (I3):
FFVPALS = C ^ nR3I3 where C is an empirical constant determined to be approximately 0.0018 nm" .
[0211] The membranes were measured on an EG&G Ortec fast-fast coincidence system using 22NaCl (~ 1.5 x 106 Bq) as the source of positrons which was sealed in a Mylar envelope. The membranes were cut and stacked into 2 mm thick bundles and placed either side of the positron source. The measurements were taken under vacuum (1 x 10"5 torr) with a minimum of 5 files collected at 4.5 x 106 integrated counts per file for each membrane. A source correction of 1.48 ns and 3.033% was subtracted from each spectra. The spectra were deconvoluted using LT v.9 software. Each spectrum was fitted to 4 components with the first 2 components fixed to 0.125 ns (Para-positonium, p-Ps, due to a bound state of opposite spin) and approximated to 0.4 ns (free annihilation). The 3rd and 4th component was due to o-Ps annihilation events indicating the presence of 2 distinct pore sizes within the membranes.
Example 1
Synthesis of poly(l,4-butadiene)- >-polydimethylsiloxane- >-poly(l,4-butadiene) (BDB) triblock copolymers
Figure imgf000053_0001
PBD-b-PDMS-b-PBD (aslo referred to as "BDB")
[0212] This Example describes the synthesis of BDB triblock copolymers with varying molecular weights.
[0213] The anionic polymerization of 1,3-butadiene was initiated by sec-BuLi in
cyclohexane at 50 °C to obtain 1,4-polybutadiene (PBD). Cyclohexane (100 mL) and 1,3 butadiene (10 mL, 0.114 mol; purified and stored as described above) were vacuum transferred in a schlenk reactor. The schlenk reactor was then transferred in the glove box where 0.02 mL of sec-BuLi (0.000213 mol) were added. The reactor was immediately placed in an oil bath preheated at 50 °C. The reaction was allowed to proceed for 18 hours. The reactor was then transferred in the glove box and a sample was removed. The sample was quenched by introducing an excess of methanol and was characterized by 1H NMR and GPC.
[0214] The anionic ring opening polymerization (ROP) of D3 was carried out using a two- step procedure. First, D3 monomer (26.6 g, 0.120 mol; purified as described above) was added to the schelnk reactor, and the reactor was left in contact with the living PBD anions overnight.
This is the initiation step and approximately one D3 monomer is added to each living chain. Subsequently, THF (100 mL; purified and stored as described above), which serves as the promoter, was vacuum transferred in a graduated ampule. The ampule was transferred in the glove box and the THF was added to the polymerization reactor (cyclohexane/THF: 50% v/v). The reactor was left at room temperature for 90 minutes. This results in propagation, which was allowed to proceed for 90 minutes at room temperature (30-50% monomer conversion). Then, the reactor was removed from the glove box, and emerged in a chiller with a temperature pre-set at -20 °C. The polymerization was left for 72 hours, and complete conversion of the monomer was confirmed by 1H NMR spectroscopy. The reactor was then transferred back into the glove box.
[0215] The BDB triblock copolymer was prepared by coupling the living poly(l,4- butadiene)-b-polydimethylsiloxanyl lithium polymer chains with 1,2-bis-
(dimethylchlorosilyl)ethane. Specifically, l,2-bis(dimethylchlorosilyl)ethane (0.046 g, 0.000213 mol; purified as described above) were added to the reactor. The coupling reaction was left for 45 minutes and then excess of trimethylchlorosilane was added to terminate any uncoupled polymer chains. The polymer was precipitated 6 times in methanol and dried under vacuum.
[0216] Finally, for long term storage, the polymer was dissolved in cyclohexane and butyl hydroxyl toluene (BHT) was added as an inhibitor. Then cyclohexane was removed under vacuum and the polymer/BHT mixture was stored at -20 °C. The volume fractions of the PDMS block of the BDB and EDE copolymers ( ^PDMS ) were estimated using monomer volumes of
0.111 nm3, 0.138 nm3 and 0.119 nm3 for PBD, PDMS and PE, respectively.
[0217] The characteristics of the four BDB triblock copolymers used in this study are summarized in Table 1. Samples in the table are labeled as "BDBX-Y", where X is the number averaged molecular weight of the copolymer, and Y is the PDMS volume fraction. 1H NMR spectroscopy analysis of the final product was used to calculate the molar ratio between the polybutadiene and polydimethylsiloxane monomeric units. See FIG. 3A.
Table 1. Molecular characteristics of the PBD homopolymers and BDB triblock copolymers synthesized.
Polymer Precursor Mn exper ^PDMS Mw/Mn
(Kg/mol)
PBD32 - 32 - 1.03 PBD49 49 1.04 PBD66 66 1.03 BDB 119-43 PBD32 32-55-32 0.43 1.21 BDB 156-23 PBD66 66-44-66 0.23 1.19 BDB200-48 PBD49 49-102-49 0.48 1.28 BDB335-78 PBD32 32-271-32 0.78 1.14
[0218] FIG. 3B shows GPC traces of a typical PBD precursor (prior to adding D3 monomer) and the BDB triblock copolymer obtained from the corresponding precursor. Both samples show predominantly one narrow GPC peak with clear shift toward higher molecular weights after the addition of the PDMS block and coupling. The dispersity, D, of the BDBX-Y was 1.14 which suggests high selectivity toward the ring opening polymerization reaction at high conversion of the monomer under the conditions specified above. The molecular weights of the BDB copolymers synthesized ranged from 119 to 335 kg/mol, PDMS volume fractions ranging from 0.23 to 0.78, and D ranging from 1.14 to 1.28 (see Table 1 above).
Example 2
Synthesis of pol ethylene- » -pol dimethylsiloxane-Z> -polyethylene (EDE)
Reaction 1: TSH thermolysis f IN¾H2 TPA HEAT N=N + ^ ¾> + TPAH
II
O O
p-Toluenesulfonyl hydrazide Diazene p-Toluenesulfinate anion
Reaction 2 : PBD hydrogenation
Figure imgf000056_0001
Reaction 3 : Diazene disproportionation
Diazene
disproportionation H, 1
2 H =N, H K3 „. N2 + H N-N
' I
Reaction 4 : PDMS degradation
Figure imgf000056_0002
[0219] This Example describes the synthesis of EDE triblock copolymers with varying molecular weights. In the first reaction depicted in the reaction scheme above, the thermolysis of p-toluenesulfonyl hydrazide (TSH) yielded in the formation of diazene and p-toluenesulfinate anion species. In the second reaction depicted in the reaction scheme above, hydrogenation of BDB was performed, wherein diazene then donates two hydrogen atoms to each double bond of the PBD monomeric units. [0220] The hydrogenation reactions in this example were generally performed as follows:
The hydrogenation reaction (reaction 2 in the reaction scheme above) was carried out in a 1L three-neck round bottom flask which was equipped with magnetic stirring, a reflux condenser, a thermometer and a stopper. The apparatus was supplied with positive pressure of dry argon. Predetermined amounts of BDB block copolymer and o-xylene were added, and the mixture was left to stir for 1 hour at 60 °C. This resulted in the complete dissolution of the polymer.
Predetermined amounts of p-toluenesulfonyl hydrazide and tripropylamine were added to the flask and the temperature was raised to the desired set point. The reaction was quenched by precipitating the product in ice cold methanol. Various reaction conditions were tested for the hydrogenation reaction, as discussed further below.
Study 1
[0221] 2 equivalents of p-toluenesulfonyl hydrazide (TSH) and 2 equivalents of the tertiary amine are used per equivalent of PBD double bonds. The polymer concentration was 0.2 g/L in o-xylene and the reaction was allowed to proceed in refluxing o-xylene (135-140 °C) for 4 hours. The hydrophilic impurities in the product were removed by extraction in water (3 repeats), the polymer was obtained by precipitation of the remaining organic phase in methanol (3 repeats).
[0222] The characterization of the product by 1H NMR spectroscopy at 353 K in deuterated toluene indicated the hydrogenation was complete by the disappearance of the polybutadiene signals and appearance of the polyethylene characteristic signal at 1.36 ppm. The integration of the PDMS methyl protons at 1.03 ppm and the polyethylene protons at 1.36 ppm agreed with the expected molar ratio of the two monomeric units. However, when the same polymer was precipitated in THF (3 repeats), the integrated PDMS signal at 1.03 ppm was suppressed by a factor of about 12 compared to the polymer precipitated in methanol (entry 1, FIG. 4). In addition, the polymer precipitated in methanol was observed to be a sticky solid while that precipitated in THF was a granular powder.
[0223] These results indicate that exposure of the BDB precursor to the standard
hydrogenation conditions resulted in fragmentation of the PDMS block. Additionally, 1H NMR spectroscopy signatures of this fragmentation are masked if the polymer is obtained by standard precipitation in methanol. Methanol and water were non-solvents for both PE and PDMS.
Therefore, the standard aqueous work up and precipitations in methanol cannot separate PE-rich and PDMS-rich fragments. In contrast, THF was observed to be a non-solvent for semi- crystalline PE, but a good solvent for PDMS. Therefore, precipitation in THF was observed to remove PDMS fragments.
Study 2
[0224] Commercially available PDMS homopolymer with average molecular weight of 63 kDa was exposed to the hydrogenation conditions as follows: a ratio of 2 mol TSH and 2 mol amine/mol of olefin was used to achieve > 99% hydrogenation. The reaction was left for 4 hours at 140 °C. The starting material and product were characterized by GPC (see FIG. 4).
[0225] The product showed a significant shift to higher retention time compared to the starting material, indicating the partial degradation of PDMS during the test reaction conditions. It must be pointed out that the scission of PDMS chains during the hydrogenation of BDB not only alters the block ratio between PDMS and PE but also changes the architecture of the final product from ABA type triblock to an AB diblock copolymer resulting in severe alteration of the product's properties.
[0226] The addition of large excess of tripropylamine (TPA) as a proton scavenger was found to affect the efficacy of the hydrogenation. The hydrogenation reaction mixture now contained two nucleophiles, the p-toluenesulfinate anion and the tripropylamine. The susceptibility of the siloxane bond to TPA was tested by performing a blank reaction where the BDB precursor polymer was heated at 135 °C in the presence of only, the weakly nucleophilic TPA, for 4 hours (no TSH was present). In this case, 1H NMR and GPC analysis of the purified product showed no evidence of degradation.
[0227] This result suggests that p-toluenesulfinate anion generated by the decomposition of TSH was most likely the species attacking the siloxane bonds. Thus, maintaining the lowest possible concentration of the p-toluenesulfinate anion while efficiently hydrogenating polybutadiene affected the synthesis of EDE copolymers.
Study 3
[0228] The hydrogenation reaction conditions (reaction temperature, reaction time, initial concentration of TSH and BDB precursor) were varied and are summarized in Table 2 below. The purified product after THF precipitations was characterized by 1H NMR spectroscopy (see FIG. 5). Table 2 below summarizes the results of six reactions. Table 2. Molecular characteristics of the final products for different hydrogenation conditions of BDB335-78.
Entry T Reaction TSH Polymer PBD mol % PDMS
(° C) Time (min) concentration Concentration hydrogenation degradation
(% wt.) (% wt.)
1 140 240 20 2 >99 91
2 140 240 5 0.5 >99 34
3 115 240 5 0.5 >99 15
4 115 180 5 0.5 >99 0
5 115 180 5 2 79 18
6 115 180 20 2 >99 62
[0229] Entry 1 shows 100% hydrogenation of PBD but in 91 % mol degradation of PDMS. Reducing the TSH and polymer concentration by a factor of four was observed to reduce the PDMS mol % degradation to 34 without affecting hydrogenation, indicating that decreasing the initial TSH concentration slows down the PDMS degradation reaction (reaction 4 in the reaction scheme above). Comparison of entries 3 and 2 indicates that reducing the reaction temperature to 115 °C also reduces degradation of PDMS without affecting the hydrogenation efficacy. Entry 3 indicates slowing down the rate at which diazene active species disproportionate (note that reaction 3 is second order to diazene concentration while reaction 2 is first order to diazene concentration). In entry 4 the reaction time is reduced from 240 to 180 minutes with all other conditions identical with those used in entry 3. Under these conditions, 0 % mol PDMS degradation and 100% PBD hydrogenation were observed.
[0230] In an attempt to improve the efficiency of the hydrogenation reaction, in entry 5, the TSH ratio was increased by a factor of two with all other conditions identical with those used in entry 4. This resulted in 18 mol % PDMS degradation and 79 % PBD hydrogenation. The incomplete hydrogenation may be due to the diazene disproportionation reaction and a concomitant reduction in the concentration of the hydrogenation active species. In entry 6, the TSH concentration was increased by a factor of four relative to entry 5, and this resulted in an increase in PDMS degradation.
[0231] The characteristics of the final EDE copolymers are listed in Table 3 below. Samples are named EDEX-Y where X is the total molecular weight of the copolymer (kg/mol) and Y is the volume fraction of the PDMS block.
Table 3. Characteristics of the EDE triblock copolymers synthesized. Polymer Precursor Mnexper Mw/Mn 0PDMS (/-spacing Morphology
(Kg/mol) (nm)
EDE 124-42 BDB 119-43 34-55-34 - 0.42 20 -
EDE 187-22 BDB 156-23 71-44-71 - 0.22 37 -
EDE209-45 BDB200-48 53-102-53 - 0.45 35 Lamellar
EDE340-77 BDB335-78 34-271-34 1.14 0.77 57 -
[0232] High temperature GPC experiments were also performed to provide further insight into the nature of products formed under the reaction conditions listed in Table 2 and provide support for the proposed reaction 4 in the reaction scheme above. With reference to FIG. 6A, GPC traces of BDB335-78 before and after hydrogenation using conditions described in entry 1 of Table 2 above are provided. In this case the hydrogenation product was purified by precipitation in THF which was observed to remove PDMS-rich fragments (91 of the sample comprises PDMS-rich fragments). When the reaction was performed at the conditions described for Study 2 in Example 2 above, complete degradation of triblock copolymer chains was observed. A change in peak elution volume from 19.2 to 23 mL was observed. Elution volume of 22.5 mL corresponded to a factor of two decrease in average molecular weight (compared to 19.2 mL), suggesting that all of the triblock copolymer chains have been severed to give diblock copolymer fragments that have further degraded.
[0233] With reference to FIG. 6B, GPC traces of BDB335-78 before and after hydrogenation using conditions described in entry 6 of Table 2 are provided. In this case, the hydrogenation product was not purified. Three populations were observed corresponding to hydrogenated triblock copolymers with elution volumes ranging from 18.5 to 21.3 mL, hydrogenated diblock copolymers with elution volumes ranging from 21 to 24 mL, and PDMS fragments with elution volumes ranging from 25.8 to 29.3 mL.
[0234] With reference to FIG. 6C, GPC traces of BDB335-78 before and after hydrogenation using conditions described in entry 4 of Table 2 are provided. In this case the hydrogenation product was purified by precipitations (3 repeats) in THF. Hydrogenation under these conditions resulted in a molecular weight distribution that is indistinguishable from that of the precursor.
[0235] FIG. 7 shows SAXS profiles of the EDE membranes at room temperature. The SAXS profiles were isotropic indicating that the membrane preparation process led to the formation of randomly oriented grains. The scattering profile of the nearly symmetric copolymer, EDE209-45, is consistent with that expected from samples with lamellar
morphology. The profile contained a primary peak at scattering vector = *=0.179 nm"1 and higher order scattering shoulders at the expected locations, q=2q* and q=3q*. The scattering profiles of the other copolymers, EDE124-42, EDE187-22 and EDE340-77 contained primary scattering peaks only. The locations of the primary scattering peaks are indicated by filled triangles in FIG. 7. The domain spacing, d, of the microphase separated EDE block copolymers was calculated by the equation d=2n/q*.
[0236] FIG. 8 provides a plot of d versus Mn, the total copolymer molecular weight. SAXS profiles collected at high temperatures, well above the melting temperature of the PE blocks (up to 160 °C), were not distinguishable from the room temperature profiles.
[0237] Additional characterization results obtained by TGA, DSC and WAXS, as depicted in FIGS. 14-16, respectively. FIG. 14 shows thermogravimetric analysis (TGA) data of the purified product synthesized under the original and optimized conditions after purification by
precipitations both in methanol and THF (Table 2, entry 1 and entry 4). The TGA results show in both cases two degradation regimes. The mass loss between 410 °C and 430 °C is due to thermal degradation of the PE block whereas the mass loss observed from 440 to 580 °C is due to thermal degradation of PDMS. The TGA results of entry 1 shows that 82 wt. % of the material degrades between 410 to 430 °C and about 18 wt. % of the total weight of the polymer is lost between 440 and 580 °C. The product of entry 4 lost about 26 wt. % between 410 °C and 430 °C and 74 wt. % between 440-580 °C.
[0238] EDE340-77, the product of entry 4, was also analyzed by DSC. The presence of one endothermic peak at 102.2 °C was observed, which corresponds to the PE melting point; and an exothermic peak at 80.2 °C, which corresponds to the PE crystallization (see FIG. 15).
[0239] Free standing films could be readily formed by the synthesized EDE triblock copolymers with thicknesses as low as 15 nm by a simple solvent casting methodology. This thickness is significantly lower compared to films formed by polystyrene-b- polydimethylsiloxane-b-polystyrene, SDS, where the thinnest free standing films have been observed around 60 μιη. Analysis of these films by wide angle x-ray scattering (WAXS) revealed the presence of two Bragg peaks at 0.124 nm"1 and 0.139 nm"1 which is signature of the [110] and [200] planes of polyethylene crystalline domains (see FIG. 16). Example 3
Preparation and Use of EDE Membranes
[0240] This Example describes the preparation and use of EDE membranes. EDE (150 mg) was dissolved in cyclohexane (20 mL) and stirred at 65 °C for a minimum of 5 hours.
Subsequently the warm solution was poured on a Teflon® sheet that was preheated at 70 °C and placed on a levelled surface. To control the diameter of the films a metal tube with smoothened edges was employed as a template. The cast area was covered with aluminum foil to slow down solvent evaporation. After solvent removal (approximately 5 hours) the film was peeled off the surface and was used for further characterization.
[0241] Pervaporation experiments of ethanol/water and butanol/water mixtures were conducted on a laboratory bench test unit built by Sulzer Chemtech, Germany. The membrane was held inside a circular cell restrained with an o-ring, providing a total permeation area of 37 cm . The temperature of the feed was controlled in the range of 40 ± 1 °C. Each experiment began with approximately 2 liters of 8 wt. % alcohol/water solution in the feed tank. On the permeate side of the membrane, a vacuum of 2-3 mbar was applied using a vacuum pump (Welch, model 2014) and permeates were condensed in a trap cooled with a dry- ice/ isopropanol mixture at -80 °C. After starting the feed pump, the system was allowed to attain steady state for 1 h before permeate samples were collected.
[0242] FIGS. 9A and 9B show the dependence of ethanol (FIG. 9A) and water (FIG. 9B) permeabilities on PDMS volume fraction, PDMS . Ethanol and water permeabilities were normalized with (ΡΕ/$™Π5 and Pw/$rans), which accounts for the different volume fraction of PDMS in each block copolymers. The
Figure imgf000062_0001
and Pw/$rans values for EDE membrane with rans =0.22 were 4.6x10
Figure imgf000062_0002
and
increased with increasing -12 -12 m 2
^rans and reached values of 8.9x10" and 9.0x10" mol m/ s Pa for the EDE membranes with $rans of 0.61. Samples with lamellar morphology exhibit lower A/( rans (i=E or W) normalized permeabilities than those with cylindrical morphology. The normalized ethanol and water permeabilities that were measured for SDS membranes under the
-12 -12 2
same conditions were 8.4x10"" and 9.3x10"" mol m/m" s Pa and for cross linked PDMS membranes were 6x10 -"1"2 and 10x10 -"1"2 mol m/m 2" s Pa. [0243] FIG. 10 shows the dependence of membrane separation factor, <¾w, on rans- From these data, <¾w was not observed to be a strong function of morphology in this system. The membrane separation factor for EDE membranes ranges from 0.75 to 0.98 for all the samples.
[0244] Permeability through a strongly microphase separated block copolymer can be expressed as:
Figure imgf000063_0001
where 0trans is the volume fraction of the transporting phase, Pi o is the intrinsic permeability of the pure transporting phase, and /is a factor that accounts for the morphology of the microphase separated block copolymers, for permeability of water (W), ethanol (E), or butanol (B). For cylindrical systems 7=1 because there is a continuous transporting phase. For lamellar systems =2/3 because, on average, one third of the lamellar grains will be oriented perpendicular to the direction of transport. The equation above assumes that transport occurs exclusively in one of the microphases.
EDE membranes with increased free volume
[0245] Additionally, EDE/PDMS blends were prepared using a solvent casting methodology on heated stage to control film temperature. Solutions of EDE, PDMS, and cyclohexane were prepared at 70 °C onto a porous Teflon® substrate at a concentration of 0.05 g EDE per mL of cyclohexane. The resultant films, with thicknesses in the 5-40 μιη range, were dried in a vacuum oven, ^PDMS is defined as the PDMS volume fraction in the supported membranes and thus ^PDMS - PDMS, as the fraction of volume occupied by the PDMS homopolymer in the EDE/PDMS mixture. In this Example, a is defined as the ratio of the molecular weight of the PDMS homopolymer to that of the PDMS in the block copolymer (the former is 14 kg moF1). For the blends at any given (^PDMS- ^DMS) the same PDMS homopolymer is added regardless of a. The polymers are named EDE XX-YY/ZZ where XX is the total average molecular weight of the copolymer, YY is the PDMS volume fraction, and ZZ is the additional PDMS volume fraction ( ^PDMS- ^PDMS) -
[0246] Table 4 shows the characteristics of supported membranes that were fabricated by blending EDE triblock copolymer with a PDMS homopolymer.
Table 4. EDE/h.PDMS blend characteristics used in this study. Polymer 0PDMS ^PDMS Mn (Kg/mol) a
EDE 187-22/8 0.22 0.30 14 0.32
EDE187-22/13 0.22 0.35 14 0.32
EDE 149-26/7 0.26 0.33 14 0.33
EDE149-26/13 0.26 0.39 14 0.33
EDE 124-42/3 0.42 0.45 14 0.24
EDE 124-42/6 0.42 0.48 14 0.24
EDE209-45/4 0.45 0.49 14 0.14
EDE209-45/13 0.45 0.58 14 0.14
EDE397-61/4 0.61 0.65 14 0.055
EDE397-61/7 0.61 0.68 14 0.055
[0247] The supported membranes were then exposed to a number of washing cycles. First the supported membranes were immersed in THF to dissolve out PDMS homopolymer chains. Then, the membrane was immersed in methanol. Three such cycles were performed for each one of the supported membranes. In all cases, the difference in mass of the films, measured before and after washing and subsequent drying steps, was within experimental error of the mass of homopolymer PDMS added in the first step (+ 2%). By removal of the PDMS homopolymer from the EDE membrane the creation of extra free volume was achieved. The free volume was assumed to be equal with the volume that the PDMS homopolymer was occupying prior to dissolution (^PDMS- ^DMS)-
[0248] FIGS. 12A and 12B show ethanol (FIG. 12A) and butanol (FIG. 12B) normalized permeabilities as a function of rans - The red circles indicate the permeability of the membranes exposed to three washing cycles. The black triangles show the theoretical increase in ethanol and butanol permeability for increased PDMS volume fraction in the membrane (while the red circles show the effect of 'exchanging' the extra PDMS volume with free volume as measured by pervaporation experiments).
[0249] The measured permeabilities for EDE396-61 increased to 9.79 for ethanol and 36.29 for butanol when the extra free volume fraction was 0.04 and to 11.1 for ethanol and 45.15 for butanol when the extra free volume fraction was 0.07. These results show a 30 % increase in ethanol and 37 % in butanol permeability. Table 5 summarizes the data for this study.
Table 5. Permeabilities for different (^PDMS- ^PDMS) in the transporting phase after removal of PDMS homopolymer.
EDE/h.pdms
0 12 supported (^PDMS- PBxl0 12 PExl0 12 Pwxl
a
(mol m/m s Pa) membranes <¾>DMs) (mol m/m s Pa) (mol m/m s Pa)
EDE397-61/4 0.04 0.055 36.29 9.79 12.49
EDE124-42/3 0.03 0.24 34.43 10.49 12.28
EDE209-45/4 0.04 0.14 - 10.71 10.94
EDE397-61/7 0.07 0.055 45.15 11.1 12.4
EDE124-42/6 0.06 0.24 41.34 10.94 13.0
EDE149-26/7 0.07 0.33 40.85 7.20 8.15
EDE209-45/13 0.13 0.14 - 12.25 12.56
EDE187-22/8 0.08 0.32 - 6.6 8.82
EDE149-26/13 0.13 0.33 35.12 6.31 8.15
EDE187-22/13 0.13 0.32 - 6.65 9.09
[0250] With reference to FIG. 13, ethanol/water and butanol/water selectivities are plotted versus $rans- Ethanol selectivity values fluctuated within error bars. Butanol selectivity remained the same (within error bars) for 0.03 extra free volume fraction but increased up to 3.6 for 0.07 extra free volume.
Example 4
Preparation of EDE Membranes with Artificial Free Volume
[0251] This Example demonstrates the preparation and characterization of a series of EDE membranes with artificial free volume.
[0252] The EDE/PDMS blend polymer membranes were prepared following procedure similar to that described in Example 3. Briefly, solutions of EDE, PDMS, and cyclohexane (0.08 g EDE per mL of cyclohexane) were cast onto a porous Teflon® substrate at 70 °C. The resulting films had thicknesses in the 20-30 μιη range. They were dried in a vacuum oven for approximately 16 h at room temperature. This was followed by drying and annealing the films for 24 h at 130 °C. The blended membranes were immersed in THF for five minutes to dissolve out PDMS homopolymer chains. Then the membranes were immersed in methanol for 5 minutes. Three such cycles were performed on each membrane, and the films were dried at room temperature either in a fume hood or in a vacuum oven. In all cases, the difference in mass of the films, measured before and after washing and subsequent drying steps, was within experimental error of the mass of homopolymer PDMS added in the blending step (+ 5%). The complete removal of the homopolymer was confirmed by integration of the 1H NMR
spectroscopy signals corresponding to PE and PDMS obtained from solutions of the dried films using deuterated cyclohexane as the solvent at 70 °C. For consistency, the neat EDE samples with no added homopolymer were subjected to the same processing steps as the blended samples.
[0253] Table 6 summarizes the characteristics of the polymer membranes. The polymers are named EDE XX-YY/ZZ, where XX is the total average molecular weight of the copolymer, YY is the PDMS volume fraction percent in the pure block copolymer, and ZZ is the additional PDMS volume fraction percent (100 x
Figure imgf000066_0001
Table 6. Characteristics of polymer membranes studied in the present work.
Figure imgf000066_0002
Molecular weights obtained by combination of gel permeation chromatography and H NMR
2 3 spectroscopy; PDMS volume fraction in the neat and composite membranes; Morphologies obtained by small angle X-ray scattering and transmission electron microscopy; 4Domain spacing obtained by small angle X-ray scattering; 5Volume fraction of PDMS homopolymer in the PDMS microphase of the composite membranes.
[0254] Following the THF and methanol washing steps, the films were peeled off from the Teflon® support and small angle X-ray scattering (SAXS) measurements taken. FIGS. 20A and 20B show background-corrected SAXS profiles for the two series of dried films that were studied. Sample EDE129-41 exhibited a broad primary scattering peak superposed on a monotonically decreasing background, and no higher order peaks. The center-to-center distance between adjacent PDMS microdomains, JEDE, is estimated to be JEDE = Ijtiq = 17.4 nm where q is the magnitude of the scattering vector at the primary scattering peak. Without wishing to be bound by any theory, the absence of higher order peaks and the presence of broad primary peaks indicate the presence of a periodic structure with little long range order. The SAXS profiles obtained from samples EDE129-41/9 and EDE129-41/17, which were samples with artificial free-volume, were qualitatively similar to EDE129-41, the sample without free volume (FIG. 20A). The creation of artificial free-volume resulted in shifts toward lower q values, indicating an increase in d.
[0255] Sample EDE129-41/9 had άΈΌΈ = 18.5 nm, and sample EDE129-41/17 had άΈΌΈ = 19.7 nm. If it is assumed that the samples have a lamellar morphology and that all of the observed increase in <iEDE occurs in the PDMS microdomains, then the SAXS data indicate expansions of 6.3% and 13.8% in EDE129-41/9 and EDE129-41/17, respectively. This expansion is consistent with the presence of artificial free-volume. The SAXS intensity of mesoporous films obtained by templated block copolymer assembly is much higher than that of pure block copolymers due to the increased scattering contrast between mesoporous voids and polymer. The similarity of all of the SAXS profiles shown in FIG. 20A indicate mesoporous structure is not present in the films.
[0256] The SAXS profiles shown in FIG. 20B for the series of samples based on EDE209-45 also indicate mesoporous structure is not present in the films. In addition to the primary scattering peak, higher order peaks were observed at 2q and 3q , consistent with a lamellar morphology. The JEDE in this series of membranes increased from JEDE = 32.2 nm for EDE209- 45 to JEDE = 33.5 nm for sample EDE209-45/7 and dEOE = 34.9 nm for sample EDE209-45/29, corresponding to an expansion of 4.0% and 8.3%, respectively. No background subtraction was used for the analysis of EDE209-45 samples.
[0257] FIGS. 21 A and 21B show dark- field transmission electron microscopy (TEM) images of cryo-microtomed samples of membranes EDE129-41 and EDE129-41/17, respectively. Both samples exhibit a lamellar morphology with little long-range order, consistent with the SAXS data (FIG. 20A). The dark lamellae represent the polyethylene-rich microdomains, while the bright lamellae represent the PDMS-rich microdomains. The TEM images are also consistent with the absence of a mesoporous structure.
[0258] The free-volume content of the EDE129-41 series was analyzed directly by positron annihilation lifetime spectroscopy (PALS). This technique enables determination of the size and relative concentration of free-volume elements by measuring the intensity (/3) and lifetime (¾) of the ortho-positronium states (oPs). A description of the technique and the approach used for analyzing PALS data may be found in Merkel TC, Freeman BD, Spontak RJ, He Z, Pinnau I, Meakan P, Hill AJ; Sorption, transport, and structural evidence for enhanced free volume in poly(4-methyl-2-pentyne)/fumed silica nanocomposite membranes, Chemistry of Materials (2003), 15, pages 109-123. The spectra of the PALS signals from all of the tested samples were consistent with a linear sum of two exponential functions, indicating the presence of free- volume elements with two distinct sizes.
[0259] FIG. 22A shows results of PALS analysis for samples EDE129-41, EDE129-41/9 and EDE129-41/17. The neat EDE129-41 sample exhibits two populations of free-volume elements centered around cavities with diameters of 0.4 and 0.8 nm. The intensities at the peaks of the distributions corresponding to the small and large cavities are shown in FIGS. 22B and 22C, respectively. The intensity corresponding to the larger cavities increases with increasing /ADD, while that corresponding to the smaller cavities decreases with increasing /ADD- The larger cavities have the largest effect on the distribution functions shown in FIG. 22A.
[0260] The volume of a given type of cavity labeled , ¼, was calculated by assuming a spherical morphology. The fractional free-volume in the films, FFV, is given by
Figure imgf000068_0001
where N; is the number density of cavities of type . N; was estimated based on relationship = x /i where A is an empirical constant equal to 0.0018, and k is the PALS intensity corresponding to cavities of type (the ordinate in FIG. 22A).
[0261] The fractional free volume of EDE129-41 was found to be 13.9 %. The EDE block copolymer contains two types of microdomains with different free-volume characteristics. In order to account for contributions from the polyethylene-rich microdomains, a polyethylene (PE) homopolymer was synthesized using the same protocol that was used for the synthesis of the triblock copolymers, and the free- volume of this homopolymer was measured by PALS. The /; versus <¾ curve obtained is shown in FIG. 26.
[0262] The FFV of pure PE was determined to be 5.4 % . The FFV of PDMS-rich microphases in the triblock membrane samples was estimated using the following equation:
_ FFV— FFVPE ΦΡΕ
^PDMS
[0263] The equation for FFVPDMS assumes that the PE-rich microphase in EDE contains the same fractional free volume as the PE homopolymer. Polyethylene is a semicrystalline polymer, and it is generally assumed that the free-volume elements reside primarily in the amorphous regions. The enthalpy of melting for each of the samples was measured using differential scanning calorimetry (DSC). The PE homopolymer, the neat EDE 129-41, and samples with artificial free- volume all showed percent crystallinities of about 28 %. Based on the equation for FFVPDMS above, the FFV of the PDMS-rich microphase in EDE129-41 is 26.7 %.
[0264] The PALS data from samples with artificial free-volume, EDE129-41/9 and EDE129- 41/17, revealed two populations, as shown in FIG. 22A. The intensity of the population with large cavities in these samples is larger than that of the neat EDE129-41. The PALS analysis described above was performed on the samples with artificial free-volume. This analysis indicates that VPDMS of EDE129-41/9 is 31.2 %, while that of EDE129-41/17 is 33.9 %.
These values are higher than that obtained from neat EDE129-41 (26.7 %).
[0265] FIG. 27 depicts a plot of the actual additional free volume obtained ( AFV) versus the fraction of the PDMS microdomains occupied by PDMS homopolymer (/ADD, the theoretical artificial free volume). This plot indicates the procedure described above can successfully create actual artificial free volume. A linear fit of the data through the origin indicates that /AFV = 0.44 X/ADD, indicating that roughly half amount of the volume originally occupied by the PDMS polymer chains is converted into artificial free-volume. Without wishing to be bound by any theory, the free-volume of a polymeric phase was increased without alteration of any other chemical characteristic of that phase.
[0266] It may be instructive to compare the fractional free volume achieved by the above methodology to cross-linked PDMS and other microporous materials. Literature values for cross-linked PDMS range from 15-25 % depending on cross linking density and method of cross-linking. Polymers with intrinsic microporosity (PIMs) and disubstituted polyacetylenes typically contain FFV in the range of 25-35% (these values correspond to free- volume of these materials before aging). The highest value of VPDMS obtained in the above study compares favorably with the values obtained in PIMs. The overall FFV in the films is somewhat lower due to the presence of the polyethylene microphase.
Example 5
Use of EDE Membranes with Artificial Free Volume
[0267] This Example demonstrates the use of a series of EDE membranes with artificial free volume in purifying two model mixtures relevant to biofuel production, butanol/water (1.5 wt. % butanol) and ethanol/water (8 wt. % ethanol) by pervaporation. [0268] The EDE membranes used were prepared and characterized following the procedure as described in Example 4 above. Pervaporation experiments of ethanol/water and butanol/water mixtures were conducted on a laboratory bench test unit built by Sulzer Chemtech, Germany.
The membrane was held inside a circular cell restrained with an o-ring, providing a total
9
permeation area of 37 cm . The temperature of the feed was controlled in the range of 40 ± 1 °C. Each experiment began with approximately 2 liters of 8 wt. % alcohol/water solution in the feed tank. On the permeate side of the membrane, a vacuum of 2-3 mbar was applied using a vacuum pump (Welch, model 2014) and permeates were condensed in a trap cooled with a dry- ice/ isopropanol mixture at -80 °C. After starting the feed pump, the system was allowed to attain steady state for 1 h before permeate samples were collected. For each polymer, two different membranes were prepared, and pervaporation experiments were repeated twice for each membrane. The average values of the four runs are reported and the standard deviation is taken to be the uncertainty of the measurements.
[0269] Permeate samples were weighed to determine the mass permeated through the membrane during the experiment. The feed composition was fixed at 8 wt. % for ethanol and 1.5 wt. % for butanol. Changes in feed composition due to pervaporation were negligible due to small amounts permeating through the membrane. Flux of water, ethanol or butanol was calculated using the equation,
, =_*-!_,
AATC 9
where M[ is the mass of individual permeant, A is the permeation area (37 cm ) and Δτε is the permeate collection time. Subscript i=E is ethanol, B is butanol, and W is water. Membrane permeability, P;, was calculated from the following equation:
Figure imgf000070_0001
where t is the membrane thickness, χλ is the feed mole fraction, γλ is the activity coefficient, ρ . Άΐ is the saturated vapor pressure, yt is the permeate mole fraction and p is the permeate pressure. Values of yi were determined by analyzing permeate samples by 1H NMR
spectroscopy with deuterated acetone (acetone-d6) as the solvent. The activity coefficients were calculated using the Van Laar coefficients obtained from Gmehling J, Onken U, Arlt W, and Rarey-Nies JR, Vapor-liquid Equilibrium Data Collection, Dechema, (1988). The saturated vapor pressure was determined using the Antoine equation. The units of mol m/(m2 s Pa) are used to report PE or Pw.
[0270] The butanol, ethanol and water permeabilities (PB, PE and Pw) through the membranes can be expressed as:
Figure imgf000071_0001
where $rans accounts for the different volume fractions of PDMS-rich transporting phase that includes the theoretical volume fraction of the added homopolymer (/ADD) in each block copolymer, P^- 0 is the intrinsic permeability of the pure transporting phase, and m is a
morphology factor that accounts for geometric constraints on diffusion. The equation assumes that transport occurs exclusively in one of the microphases. For lamellar systems, m=2/3. All of the tested membranes had a lamellar morphology.
[0271] Since P; is measured and m and ^DMS are known, the preceding equation is used to determine the intrinsic permeability of the transporting phase in the membranes, PB,0, ΡΕ,Ο, PW,O- FIG. 24 shows the dependence of PE,0 (left y-axis) and PB,0 (right y-axis) on /ADD (top x-axis). The intrinsic butanol and ethanol permeabilities for the neat EDE samples thus obtained were
-12 -12 2
ΡΕ,Ο = 8.5x10" and PB,o = 26 xlO" mol m/m s Pa. These values are higher than typical literature values for cross- linked PDMS (PE= 6.0xl0~12mol m/m2 s Pa and PB = 21xl0"12mol m/m2 s Pa).
[0272] The introduction of artificial free-volume results in a large increase in butanol and ethanol permeabilities (see FIG. 23). Membrane EDE129-41/17 showed ethanol permeability of
10.8 xlO -"12 and butanol permeability of 37.5 xlO -"12 , an increase of 27% and 44% compared to neat EDE samples, respectively.
[0273] As actual artificial free- volume /AFV is a linear function of added homopolymer volume fraction /ADD, the data in FIG. 27 can be used to investigate the dependence of permeability on artificial free- volume. The bottom x-axis of FIG. 23 was used to quantify the effect of actual artificial free-volume on intrinsic butanol and ethanol permeabilities. Butanol and ethanol permeabilities through EDE129-41/9 and EDE129-41/17 were measured two months after the data shown in FIG. 23 were gathered. These permeabilities were within experimental error of those reported in FIG. 23. This demonstrates the stability of artificial free-volume created by block copolymer aggregation.
[0274] The efficacy of a reverse selective membrane is determined by both absolute flux and selectivity, <¾jW (i=B or E)
Figure imgf000072_0001
[0275] The effect of artificial free-volume on selectivity is shown FIG. 24, where <¾jW and <¾w are plotted versus /AFV- The plot in FIG. 24 indicates that the enhancement in flux reported in FIG. 23 is not obtained at the expense of selectivity. In fact, selectivity increases slightly with increasing /AFV- The data in FIG. 24 indicate that the actual artificial free-volume created by the self-assembly process is more hydrophobic than that present in cross-linked PDMS. The dielectric constant of vacuum (8.85 x 10"12F/m) is lower than that of PDMS (2.2 x 10"11 F/m). The data in FIGS. 23 and 24 show that the transport of hydrophobic molecules, such as butanol, is increased by the presence of artificial free-volume relative to that of polar molecules, such as ethanol and water. Without wishing to be bound by any theory, the performance of EDE membranes with artificial free-volume is thus not subject to the typical trade-off of flux versus selectivity.
[0276] In summary, this example demonstrates that it is possible to increase the size and concentration of free- volume cavities in a controlled fashion by block copolymer self-assembly. Thus obtained are membranes that are chemically similar to their precursors but contain systematically varied levels of free-volume. The utility of these materials was demonstrated by testing membranes for butanol/water and ethanol/water mixtures, separations that require reverse selectivity and are relevant to biofuel production. The presence of artificial free-volume resulted in increase of both butanol and ethanol permeabilities without adversely affecting selectivity.

Claims

1. A membrane, comprising a plurality of poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers, wherein each triblock copolymer comprises a first polyalkylene end block and a second polyalkylene end block separated by a polydialkylsiloxane block; wherein at least a portion of the plurality of triblock copolymers is aggregated to form one or more polyalkylene-rich microphases and one or more polydialkylsiloxane- rich microphases.
2. The membrane of claim 1, wherein the membrane has one or more of the following properties (i) to (vii):
(i) a polydialkylsiloxane block volume fraction (^DMS) between 0.2 and 0.95;
(ii) a domain spacing (d) between 10 nm and 90 nm;
(iii) a molecular weight between 50 kg/mol and 400 kg/mol;
(iv) an average thickness of at least 1 μιη;
(v) an ethanol permeability, normalized with the volume fraction of the transporting phase, of between 7 mol m/m 2 s Pa and 14 mol m/m 2 s Pa;
(vi) a ratio of the permeability of one or more organic compounds to the permeability of water of between 1.0 to 4.0; and
(vii) is free standing.
3. The membrane of claim 1 or 2, further comprising one or more polydialkylsiloxane homopolymers, wherein at least a portion of the one or more polydialkylsiloxane homopolymers and at least a portion of the plurality of triblock copolymers are aggregated to form the one or more polydialkylsiloxane-rich microphases; wherein the triblock copolymer has a theoretical artificial free volume (/ADD); wherein the theoretical artificial free volume is the volume fraction of one or more polydialkylsiloxane-rich microphases occupied by the at least a portion of the one or more polydialkylsiloxane homopolymers; and wherein the theoretical artificial free volume is between 0.02 and 0.80.
4. The membrane of claim 1 or 2, wherein the membrane has an actual artificial free volume, wherein the actual artificial free volume is the free volume of the membrane in addition to the free volume associated with the polydialkylsiloxane block volume fraction
Figure imgf000074_0001
wherein the actual artificial free volume is between 0.02 and 0.45.
5. The membrane of claim 1 or 2, wherein the membrane has a non-equilibrium free volume, wherein the non-equilibrium free volume is the difference in total free volume measured before annealing and the total free volume measured after annealing.
6. A membrane, comprising a plurality of poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers and a plurality of polydialkylsiloxane homopolymers, wherein each triblock copolymer comprises a first polyalkylene end block and a second polyalkylene end block separated by a polydialkylsiloxane block; wherein at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of polydialkylsiloxane homopolymers are aggregated to form one or more polyalkylene -rich microphases and one or more polydialkylsiloxane-rich microphases.
7. The membrane of any one of claims 1 to 6, wherein the polyalkylene is polyethylene, polypropylene, polyisoprene or polybutadiene.
8. The membrane of any one of claims 1 to 6, wherein the polyalkylene end blocks are independently optionally substituted with halo.
9. The membrane of any one of claims 1 to 6, wherein the polydialkylsiloxane is polydimethylsiloxane.
10. A supported membrane, comprising
(i) a membrane according to any one of claims 1 to 9; and
(ii) a porous support.
11. The supported membrane of claim 10, wherein the porous support is a reverse osmosis membrane, a nanofiltration membrane, or an ultrafiltration membrane.
12. The supported membrane of claim 10 or 11, wherein the porous support comprises polysulfone, polyacrylonitrile, polyvinylidene fluoride, or any combinations thereof.
13. The supported membrane of any one of claims 10 to 12, wherein the membrane has an average thickness of at least 9 μιη.
14. A method of separating one or more organic compounds from an aqueous mixture of organic compounds, the method comprising contacting the aqueous mixture with a membrane to separate one or more organic compounds from the aqueous mixture, wherein the membrane is a membrane according to any one of claims 1 to 9, or a supported membrane according to any one of claims 10 to 13; and wherein one or more of the organic compounds in the aqueous mixture selectively permeates through the membrane.
15. The method of claim 13, wherein the one or more organic compounds are selected from the group consisting of acetone, ethanol, w-butanol, isobutanol, 2-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, acetic acid, formic acid, levulinic acid, succinic acid, furfural, 5-hydroxymethylfurfural, 2-furoic acid, vanillic acid, ferulic acid, p-coumaric acid, syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid), 4-hydroxybenzoic acid,
protocatechuic acid (3,4-dihydroxybenzoic acid), homovanillic acid (2-(4-hydroxy-3-methoxy- phenyl)acetic acid), caffeic acid (3,4-dihydroxycinnamic acid), sinapic acid, propionic acid, vanillylmandelic acid, 4-hydroxymandelic acid, 4-hydroxyphenylacetic acid, 3-hydroxybenzoic acid, 2,5-dihydroxybenzoic acid, benzoic acid, vanillin, syringaldehyde, 4- hydroxybenzaldehyde, coniferyl aldehyde (4-OH-3-OCH3-cinnamaldehyde), sinapinaldehyde (3,5-dimethoxy-4-hydroxycinnamaldehyde), protocatechualdehyde (3,4- dihydroxybenzaldehyde), acetovanillone (4'-hydroxy-3'-methoxyacetophenone), acetosyringone (3',5'-dimethoxy-4'-hydroxyacetophenone), guaiacol, coniferyl alcohol (4- (3 -hydroxy- 1- propenyl)-2-methoxyphenol), hydroquinone, catechol (pyrocatechol), vanillyl alcohol (4- hydroxy-3-methoxybenzyl alcohol), eugenol, and any combinations thereof.
16. The method of claim 15, wherein the one or more organic compounds are one or more alcohols.
17. The method of claim 16, wherein the one or more alcohols are ethanol, butanol, or a combination thereof.
18. The method of claim 15, wherein the one or more organic compounds separated are selected from the group consisting of ethanol, w-butanol, isobutanol, 2-butanol, 1-pentanol, 1- hexanol, 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol.
19. The method of any one of claims 14 to 18, wherein the one or more organic compound are obtained from a renewable or biological source.
20. The method of any one of claims 13 to 18, wherein the ratio of the permeability of the one or more organic compounds to the permeability of water is between 1.0 to 4.0.
21. A method of producing a membrane, the method comprising: providing a plurality of poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers; providing a plurality of polydialkylsiloxane homopolymers; combining the plurality of triblock copolymers, the plurality of homopolymers, and a first solvent to form a polymer mixture, wherein the first solvent solubilizes at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of homopolymers; and casting the polymer mixture to produce a membrane, wherein the membrane comprises at least a portion of the plurality of triblock copolymers and at least a portion of the plurality of homopolymers.
22. The method of claim 21, further comprising annealing the membrane.
23. The method of claim 21 or 22, further comprising: contacting the membrane with a second solvent, wherein the second solvent solubilizes at least a portion of the plurality of homopolymers; and removing at least a portion of the solubilized homopolymers.
24. A poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymer comprising a polydialkylsiloxane block and polyalkylene end blocks, wherein the triblock copolymer has a molecular weight of at least 50 kg/mol, and wherein the polyalkylene is optionally substituted with halo.
25. The triblock copolymer of claim 24, wherein the triblock copolymer has one or more of the following properties (i) to (v):
(i) a polydialkylsiloxane volume fraction between 0.2 and 0.95;
(ii) a morphology capable of providing a continuous transporting phase;
(iii) a domain spacing (d) between 10 nm and 90 nm;
(iv) a cylindrical, lamellar, double diamond, or gyroid morphology; and
(v) a molecular weight between 50 kg/mol and 400 kg/mol.
26. A method of producing a poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer, wherein t is an integer greater than or equal to 2, the method comprising
hydrogenating a poly(C2t alkadiene-b-dialkylsiloxane-b-C2t alkadiene) triblock copolymer in the presence of diazene to produce the poly(Ct alkylene-b-dialkylsiloxane-b-Ct alkylene) triblock copolymer.
PCT/US2015/030213 2014-05-28 2015-05-11 Poly(alkylene-b-dialkylsiloxane-b-alkylene) triblock copolymers and uses thereof WO2015183538A2 (en)

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